United States
Environmental Protection
Agency
Office of Emergency and
Remedial Response
Washington DC 20460
EPA/540/G-88/003
OSWER Directive 9283.1-2
December 1988
Superfund
&EPA
on Remedial
Actions for
Contaminated Ground
Water at Superfund
Sites
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I I A
t'hu^:»ive 9283.1-2
ut keii^ntitil for
at
Office of Emergency and Remedial Response
U.S. Environmental Protection Agency
Washington, IDC
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Notice
Development of this document was funded by the United States Environmental Protection Agency in part under contract
No. 68-WB-0098 to CH2M HILL SOUTHEAST. It has been subjected to the Agency's review process and approved for
publication as an EPA document.
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. The Agency reserves the right to act at variance with these policies and procedures
and to change them at any time without public notice.
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Executive Summary
This document provides guidance for making key decisions in developing, evaluating, and selecting ground-water
remedial actions at Superfund sites. It provides information that can be used in the process of investigating and
assessing remedial actions for contaminated ground water and may be considered a primer on pertinent aspects of
ground-water contamination that are important to the development of sound remedies.
This guidance focuses on policy issues and the decision-making approach and highlights key considerations to be
addressed during the remedy selection process. The statutory and policy framework presented here for ground-water
remedial actions was drawn from the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA) as amended by the Superfund Amendments and Reauthorization Act (SARA)-henceforth referred to as
CERCLAand program policies to implement these acts.
The goal of Superfund ground-water remediation is to protect human health and the environment by restoring ground
water to its beneficial uses within a reasonable time frame, given the particular site circumstances. CERCLA requires
that remedial actions protect human health and the environment, meet applicable or relevant and appropriate
requirements (ARARs) as established by Federal and State standards, and be cost-effective. CERCLA also requires
the selection of remedies that use permanent solutions and treatment technologies or resource recovery technologies
to the maximum extent practicable and expresses a preference for the selection of remedies that use treatment that
permanently and significantly reduces the mobility, toxicity, or volume of hazardous substances as a principal element.
The Ground-Water Protection Strategy (U.S. EPA, 1984) plays an important role in the ground-water remedial action
decision-making process because the Superfund program generally applies the basic framework outlined in the strategy
for protecting ground water according to its current and future vulnerability, use, and value. The ground-water remedial
action approach presented in this document is consistent with the Ground-Water Protection Strategy and with the
development, evaluation, and selection of remedial alternatives linked to the characteristics of the ground water.
When remediating ground water, potential ARARs of other regulations must be met unless a waiver is used. For ground
water, the main sources of these requirements are the Resource Conservation and Recovery Act, the Safe Drinking
Water Act, and the Clean Water Act.
Before initiating remedial investigation/feasibility study (RI/FS) activities, site management planning should be
conducted. This planning identifies potential removal actions and operable units and their optimal sequence and timing.
Site management planning is a dynamic process in which refinements continue to be made throughout the RI/FS
process as a better understanding of the site is obtained. At the same time that site management planning is
conducted, scoping also occurs, during which data collection activities that will take place during the RI/FS are planned.
Cleanup levels for ground water are selected to maintain the ground water's beneficial uses. If the ground water is
potentially drinkable, cleanup levels are determined according to health-based standards for drinking water. If the ground
water discharges
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Executive Summary (continued)
into an aquatic habitat, cleanup levels may be based on those protective of aquatic life. Aggregate effects of multiple
contaminants found in ground water should be assessed to ensure that risks do not exceed protective levels.
Remedial action objectives are developed after site characterization. Remedial action objectives specify the area of
attainment, the restoration time frame, and cleanup levels. Cleanup levels should be achieved throughout the area of
attainment as quickly as is practicable considering the particular site circumstances. Factors that affect the restoration
time frame include technical feasibility, feasibility of providing an alternate water supply, the potential use and value of
the ground water, institutional controls, and the ability to monitor and control the movement of ground water. The area
of attainment includes the entire ground-water plume except for the area directly beneath any waste that is contained
and managed onsite. (Though property ownership may increase the flexibility for extending the restoration time frame,
it does not affect the specification of the area of attainment over which cleanup levels must be achieved.)
Several types of remedial action alternatives that span a range of technologies and restoration time frames should be
developed early in the FS process. Potential response approaches include the following:
! An active restoration alternative that reduces contaminant levels to required cleanup levels in the minimal time
feasible
! Additional active restoration alternatives that achieve cleanup levels over longer time frames
! A plume containment alternative that prevents expansion of the plume
! A natural attenuation alternative that includes institutional controls and monitoring
! An alternative involving wellhead treatment or provision of an alternate water supply and institutional controls
when active restoration is not practicable
The remedial action alternatives should be developed and screened on the basis of general considerations of
effectiveness, implementability, and cost. Best professional judgment should be used to identify those remedies that
meet the remedial action objectives for the site and are not disproportionately costly. Preference should be given to
alternatives that provide the most rapid restoration that can be achieved practicably.
A detailed analysis of alternatives should be conducted using the following criteria:
! Overall protection of human health and the environment
! Compliance with ARARs-waivers to ARARs are listed in CERCLA and may be warranted under specific
conditions
! Long-term effectiveness and permanence
! Reduction of mobility, toxicity, or volume
! Short-term effectiveness
! Implementability
! Cost
! State acceptance
! Community acceptance
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Executive Summary (continued)
A remedy is selected from alternatives that undergo a detailed analysis and is determined to provide adequate
protection of human health and the environment, to attain ARARs, or to provide grounds for invoking a waiver.
Within these bounds, the remedy is to be cost-effective, providing overall effectiveness that is proportional to
cost. The selected remedy will be the alternative found to provide the best balance of tradeoffs among
alternatives in terms of the nine evaluation criteria listed above. This remedy represents the maximum extent
to which permanent solutions and treatment technologies can be used practicably.
Often, the success of a ground-water remedial action is difficult to predict until the action has been initiated and
operational data have been assessed. Because of the uncertainties in characterizing contaminated ground
water, remedial actions often are selected on the basis of limited data. This guidance promotes a flexible
decision-making process for ground-water remedial actions to accommodate these uncertainties and resolve
the differences between design and actual performance. For sites at which actual performance lags behind
design performance, as measured by contaminant mass removal, for example, a determination should be made
to (1) continue the existing remedial action and revise the remedial action objectives for the site, (2) upgrade
or replace the selected remedy to meet the remedial action objectives, or (3) terminate the remedial action if
there is no longer a threat to human health or the environment. Fundamental changes in the remedial action
require modification of the Record of Decision (ROD).
Appendix A to this guidance document presents a case study, or hypothetical scenario, to demonstrate key
features of the ground-water remedial action decision process. The study focuses on the decisions that must
be made during the RI/FS and the pertinent factors affecting evaluation of alternatives and selection of a
ground-water remedy.
Appendix B presents the framework of EPA's policy for investigating and remediating multiple source plumes,
i.e., plumes caused by multiple sites (some of which are not necessarily Superfund sites). The strategy
identifies which actions might be accomplished by PRPs; it also includes schedules for enforcement functions
necessary to support PRP action.
Appendix C describes the contents of a ROD that supports an interim action. Although RODs for interim actions
need to adequately describe the rationale for the action and how the statutory criteria are met, such RODs will
often be less detailed than the RODs prepared for final remedial actions.
Appendix D presents two basic ground-water equations that can be used to estimate the restoration time frame.
Appendix E lists standards and health-based criteria that may be pertinent in setting preliminary cleanup levels.
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Contents
Page
Executive Summary iii
Exhibits x
Figures xi
Tables xii
List of Acronyms xiii
List of Definitions xv
Acknowledgments xvii
1. Introduction 1-1
1.1 Purpose and Objectives 1-1
1.2 Overview of the Remedial Process 1-1
1.3 Other EPA Guidance Documents Pertinent to Ground-Water
Remedial Actions Under Superfund 1-2
1.4 Organization of This Document 1-2
2. Statutory and Policy Framework for Ground-Water Remedial Alternatives 2-1
2.1 Introduction 2-1
2.2 Requirements and Provisions of CERCLA and the NCP 2-1
2.2.1 Applicable or Relevant and Appropriate Requirements 2-2
2.2.2 Use of Permanent Solutions and Treatment Technologies to the Maximum
Extent Practicable 2-2
2.2.3 Preference for Treatment as a Principal Element 2-2
2.2.4 CERCLA Restrictions on Establishing ACLs 2-2
2.2.5 Funding Remedial Actions 2-4
2.2.6 Evaluating Remedial Action Performance 2-4
2.3 The EPA's Ground-Water Protection Strategy and Classification Guidelines 2-4
2.4 Application of RCRA to Ground-Water Remediation 2-5
2.4.1 The Land Disposal Restrictions 2-5
2.4.2 The RCRA Ground-Water Monitoring and Response Program 2-8
2.4.3 The Subpart S Regulations 2-9
2.5 The Safe Drinking Water Act 2-9
2.6 The Clean Water Act 2-10
3. Scoping Ground-Water Remedial Activities 3-1
3.1 Introduction 3-1
3.2 Site Management Planning 3-1
3.2.1 Removal Actions 3-1
3.2.2 Operable Units 3-4
3.3 Project Planning-Data Collection Activities 3-7
3.3.1 Characterization of the Hydrogeology 3-11
3.3.2 Characterization of Contamination 3-12
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Contents (continued)
Page
3.3.3 Analysis of Plume Movement and Response 3-13
3.3.4 Assessment of Design Parameters for Potential Treatment
Technologies 3-14
3.3.5 Technical Uncertainty 3-14
4. Establishing Preliminary Cleanup Levels 4-1
4.1 Introduction 4-1
4.2 Determination of Cleanup Levels 4-1
4.2.1 Process 4-1
4.2.2 One Source of Common Health-Based Criteria: The Integrated Risk
Information System 4-2
4.3 Derivation of Chemical-Specific ARARs and TBCs 4-3
4.3.1 Maximum Contaminant Levels 4-3
4.3.2 Promulgated State Standard 4-3
4.3.3 Risk-Specific Doses for Carcinogens 4-6
4.3.4 Reference Doses 4-6
4.3.5 Health Advisories 4-6
4.3.6 Maximum Contaminant Level Goals 4-6
4.3.7 Water Quality Criteria 4-7
4.4 Assessment of Aggregate Effects 4-7
4.5 Alternate Concentration Limits 4-8
4.6 Summary 4-10
5. Developing Remedial Alternatives 5-1
5.1 Introduction 5-1
5.2 Remedial Action Objectives 5-1
5.2.1 Area of Attainment 5-1
5.2.2 Restoration Time Frame 5-2
5.3 General Response Actions 5-4
5.3.1 Active Restoration 5-4
5.3.2 Plume Containment or Gradient Control 5-7
5.3.3 Limited or No Active Response 5-7
5.4 Formulating and Screening Alternatives 5-9
5.4.1 Ground Water That Is A Current or Potential Source of Drinking Water 5-9
5.4.2 Ground Water That Is Not Current or Potential Drinking Water 5-11
6. Detailed Analysis of Alternatives and Selection of Remedy 6-1
6.1 Introduction 6-1
6.2 Evaluation Criteria 6-1
6.2.1 Overall Protection of Human Health and the Environment 6-1
6.2.2 Compliance with ARARs 6-1
6.2.3 Long-Term Effectiveness and Permanence 6-3
6.2.4 Reduction of Mobility, Toxicity, or Volume 6-3
6.2.5 Short-Term Effectiveness 6-3
6.2.6 Implementability 6-3
6.2.7 Cost 6-4
6.2.8 State Acceptance 6-4
6.2.9 Community Acceptance 6-4
6.3 Selection of Remedy 6-4
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Contents (continued)
Page
7. Evaluating Performance and Modifying Remedial Actions 7-1
7.1 Introduction 7-1
7.2 Modifying Decisions 7-1
7.3 Modifications to Records of Decision 7-1
7.4 Performance Monitoring 7-4
7.4.1 Well Locations 7-4
7.4.2 Sampling Duration and Frequency 7-4
7.4.3 Source Control Monitoring 7-4
References 8-1
Appendix A. Case Study With Site Variations A-1
Appendix B. Strategy for Addressing Ground-Water Contamination From Multiple Sources Involving
Superfund Sites B-1
Appendix C. Documenting an Interim Action C-1
Appendix D. Basic Ground-Water Equations D-1
Appendix E. Tables of U.S. EPA Water Standards, Criteria, and Guidelines for Establishing Ground
Water Cleanup Levels E-1
Appendix F. Sample Letter to Obtain Property Access F-1
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Exhibits
Number Page
3-1 Removal Action at the Cherokee Site 3-4
3-2 Identifying Operable Units 3-6
3-3 Interim Action: Alternate Source of Drinking Water 3-7
3-4 Interim Action: Preventing Further Ground-Water Degradation 3-8
3-5 Ground-Water Modeling at a Superfund Site 3-15
3-6 Using a Sensitivity Analysis 3-20
4-1 Setting Cleanup Levels at Seymour Recycling 4-8
4-2 Ground Water Discharging to Surface Water 4-11
5-1 Institutional Controls in New Jersey 5-5
5-2 Biorestoration at Biocraft Laboratories 5-7
B-1 A Multiple Source Plume in the Biscayne Aquifer B-2
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Figures
Number Page
1-1 Decision Points in the Superfund Process 1-3
1-2 Overview of the Ground-Water Remedy Selection Process 1-4
2-1 Possible Action-Specific ARARs for Ground-Water Remedial Actions 2-3
2-2 Ground-Water Classification Flow Chart 2-6
3-1 Planning and Scoping Ground-Water Remedial Activities 3-2
3-2 Removal Action Level Policy Flow Chart 3-5
3-3 Exposure Pathways Related to Ground Water 3-9
3-4 The Steps of Formulating and Implementing a Ground-Water Model 3-17
4-1 Flow Chart for Determining Site-Specific Cleanup Levels on the Basis of Existing Standards
and Criteria 4-4
4-2 Derivation of Some Standards and Health-Based Criteria 4-5
5-1 Conceptual Diagram of Waste Source, Contaminant Plume, and Attainment Area 5-2
5-2 Schematic of a Soil Vapor Extraction System 5-8
5-3 General Response Actions and Process Options for Ground Water 5-10
7-1 Predicting Remedial Action Performance from Monitoring Data 7-2
7-2 Flexible Decision Process for Ground-Water Remedial Actions 7-3
A-1 Distribution of Contaminants, Hypo-Thetical Site A-5
D-1 Prediction of Ground-Water Restoration Time Frame Using the Batch Flushing Model D-2
D-2 Results of Leaching Column Study for Determination of the Dynamic Leaching
Rate Constant D-2
D-3 Prediction of Ground-Water Restoration Time Frame Using the Continuous
Flushing Model D-2
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Tables
Number Page
1-1 EPA Guidance Documents Pertinent to Ground-Water Remedial Actions
Under Superfund 1-5
2-1 Schedule for implementation of the Land Disposal Restrictions 2-7
3-1 Questions to Focus Data Collection Activities 3-10
3-2 Processes and Variables Applicable to Ground-Water Modeling 3-18
3-3 Typical Technology Selection and Design Parameters 3-19
4-1 Possible ARARs and TBCs 4-3
4-2 Factors Considered When Determining Preliminary Cleanup Level 4-9
5-1 Potential Response Objectives for Ground Waters 5-2
A-1 Concentrations of Chemicals in Ground Water A-2
A-2 Evaluation of the Operable Unit Taken as an Interim Action A-4
A-3 Contaminant-Specific ARARs and TBCs A-6
A-4 Aggregate Risk A-7
A-5 Contaminants Detected in Ground Water Concentration, Toxicity, and Mobility A-9
A-6 Hypo-Thetical Site Summary A-11
A-7 Summary of Detailed Analysis Hypo-Thetical Site-Balancing Criteria A-12
A-8 Health-Based Criteria Related to Surface Water A-14
B-1 Potential Sources of Multiple-Source Ground-Water Contamination B-3
E-1 U.S. EPA Drinking Water Standards, Criteria, and Guidelines for Protection of
Human Health E-2
E-2 U.S. EPA Water Quality Criteria for Protection of Aquatic Life E-6
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List of Acronyms
ACLs Alternate concentration limits
ARARs Applicable or relevant and appropriate requirements
BAT Best available technology
BCT Best conventional technology
CAG Carcinogen Assessment Group
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CRAVE Carcinogen Risk Assessment Verification Endeavor
CWA Clean Water Act
DCE Dichloroethene
DEHP Bis(2-ethylhexyl)phthalate
DNAPL Dense nonaqueous phase liquid
DQOs Data quality objectives
DWEL Drinking water equivalent level
ERD Emergency Response Division of OERR
HA Health advisory
HI Hazard index
IRIS
ISV
Koc
Kn
Integrated Risk Information System
In situ vitrification
Organic carbon partition coefficient
Partition coefficient
LOAEL Lowest observed adverse effects level
LOEL Lowest observed effects level
MCL Maximum contaminant level
MCLG Maximum contaminant level goal
NCP National Contingency Plan
NOAEL No observed adverse effects level
NOEL No observed effects level
NPL National Priorities List
NPDES National Pollutant Discharge and Elimination System
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List of Acronyms (continued)
OERR Office of Emergency and Remedial Response
OSW Office of Solid Waste
OSWER Office of Solid Waste and Emergency Response
PA/SI Preliminary assessment/site inspection
PCE Perchloroethene.Tetrachloroethene
PHRED Public Health Review Evaluation Database
PRP Potentially responsible party
POTW Publicly owned treatment works
QSAR Quantitative structure-activity relationships
RPM Remedial project manager
RCRA Resource Conservation and Recovery Act
RfD Reference dose
RI/FS Remedial investigation/feasibility study
ROD Record of Decision
RSD Risk-specific dose
SARA Superfund Amendments and Reauthorization Act
SDWA Safe Drinking Water Act
SWMU Solid-waste management unit
TBC To-be-considered
TCA Trichloroethane
TCE Trichloroethene
TVO Total volatile organic
UIC Underground injection control
UPL Unacceptable pollutant levels
VOC Volatile organic compound
WQC Water quality criteria
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List of Definitions
Absorption
Adsorption
Applicable requirements
Area of attainment
Cleanup level
Cost-effectiveness
Dense nonaqueous phase liquid
Hot spots
Implementability
Institutional controls
Transport of a substance through the outer boundary of a medium,
frequently through biological membranes, through active transport,
passive diffusion, etc.
Bonding, frequently ionic, of a substance to soil or other medium.
A substance is said to be adsorbed if the concentration in the
boundary region of a soil particle is greater than in the interior of
the contiguous phase.
Requirements promulgated under Federal or State law that
specifically address the circumstance at a Superfund site.
The area of the plume outside the boundary of any waste to be
managed in place as part of the final remedy and inside the
boundaries of the contaminant plume.
The contaminant concentration goal of the remedial action, i.e., the
concentration of a ground-water contaminant to be achieved
through remedial action.
One of the mandates for remedial action under CERCLA. It
requires a close evaluation of the costs required to implement and
maintain a remedy as well as the selection of protective remedies
whose costs are proportional to their overall effectiveness.
A liquid that is more dense than liquid water and is not appreciably
soluble in water. Hence, the liquid forms a second phase below the
ground water.
Term used to denote zones where contaminants are present at
much higher concentrations than surrounding areas.
Implementability includes the technical and administrative
feasibility of an action as well as the availability of needed goods
and services.
Controls prohibiting or limiting access to contaminated media; may
consist of deed restrictions, use restrictions, permitting
requirements, etc.
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List of Definitions (continued)
Interim action
Operable unit
Performance evaluation
Practicability
Relevant and appropriate requirements
Remedial action objectives
Removal action
Restoration time frame
Site management planning
Sorption
Systemic effects
To-be-considered
Technical feasibility
Transmissivity
An action that initiates remediation of a site but may not constitute
the final remedy.
An overall response action that by itself eliminates or mitigates a
release, a threat of a release, or an exposure pathway.
An evaluation undertaken after remediation has been implemented
to determine the effectiveness of the remedial action.
An action is practicable from an engineering perspective if it can be
implemented within cost and time constraints, is not unreasonably
difficult or complex, and is reliable.
Requirements that, while not "applicable" to a Superfund site,
address situations sufficiently similar to a site that their use is well
suited.
Cleanup objectives that specify the level of cleanup, area of
cleanup (area of attainment), and time required to achieve cleanup
(restoration time frame).
An action that is implemented to address a direct threat to human
health or the environment.
Time required to achieve cleanup levels.
A planning phase in which the types of response approaches to be
taken to address site problems and their optimal sequence are
identified
Adsorption and/or absorption.
Effects that require absorption and distribution of the toxicant to a
target organ at which point effects are produced. Most chemicals
that produce systemic toxicity do not cause a similar degree of
toxicity in all organs but usually demonstrate major toxicity to one
or two organs.
Guidelines and criteria that should be considered when evaluating
remedial actions.
A determination that the technology can be implemented and
maintained on the basis of engineering judgment.
A measure of the amount of water that can be transmitted
horizontally by the full saturated thickness of the aquifer under a
hydraulic gradient of 1.
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Acknowledgments
We wish to acknowledge the following people who assisted in preparing this document.
Jennifer Haley/OERR Walter Walsh/OPA
Caroline Roe/OERR Craig Zamuda/OPA
Betsy Shaw/OERR Steve Nicholas/OPA
Bill Hanson/OERR
Betti Van Epps/OERR Jose Valdes/OGWP
Joanne Bahura/OSW Candice Wingfield/OWPE
Lisa Lefferts/OSW
Vern Myers/OSW Joe Freedman/OGC
David Lang/Region I Jerry Jones/RSKEL
Damian Duda/Region II Scott Huling/RSKEL
Kathy Davies/Region III
Gregg Kulma/Region V Edward Barth/HWERL
Ruth Izraeli/Region VI
Jeff Rosenbloom/Region IX Lisa Herrinton/CH2M HILL
Mike Tilchin/CH2M HILL
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Chapter 1
Introduction
1.1 Purpose and Objectives
This guidance document focuses on key issues in the
development, evaluation, and selection of ground-water
remedial actions at Superfund sites. Statutory mandates
require that remedies be protective and utilize permanent
solutions and treatment technologies to the maximum extent
practicable. Consistent with these mandates, the goal of
Superfund ground-water actions is to restore ground water to
its beneficial uses within a reasonable time frame, given the
particular site circumstances.
The principal objectives of this guidance are as follows:
! Present the analytical framework and statutory basis
for formulating ground-water alternatives
! Outline factors that should be examined to evaluate
and compare ground-water alternatives
! Highlight key considerations for selecting a
ground-water remedy
! Illustrate with a case study the remedial investigation
(Rl) and feasibility study (FS) process for ground
water
Technical aspects of ground-water investigation, evaluation,
and remediation are not discussed in detail here. Throughout
the text, however, the reader is referred to other sources that
do address these technical concerns. In addition, Geraghty &
Miller's Groundwater Bibliography (van der Leeden, 1987) lists
numerous resources, organized by subject, related to ground
water.
This document has been prepared as a resource for three
groups: (1) EPA and State remedial project managers (RPMs)
responsible for the overall scope, structure, quality, and
completeness of RI/FSs involving ground-water contamination,
(2) contractors or the Corps of Engineers that plan and
execute RI/FSs at Superfund sites with ground-water
contamination, and (3) others responsible for
preparing remedial alternatives and recommending
ground-water remedial actions at Superfund sites.
Although each Superfund site presents unique environmental
conditions and human health problems, a consistent approach
should be used when collecting and analyzing data and
developing and evaluating ground-water remedial alternatives.
The consideration of both the issues and the decision-making
approach presented here should provide reasonable
consistency in analyzing ground-water remedial action
alternatives at sites that pose similar contamination problems
and threats to human health and the environment.
1.2 Overview of the Remedial Process
The Superfund remedial process begins with the identification
of site problems during the preliminary assessment/site
inspection, which is conducted before a site is listed on the
National Priorities List; continues through site characterization
in the Rl and development, screening, and detailed analysis
of remedial alternatives in the FS; and culminates in the
selection, implementation, and operation of a remedial action.
EPA describes each step of the RI/FS process and describes
how the steps are integrated in the Guidance for Conducting
Remedial Investigations and Feasibility Studies Under
CERCLA (RI/FS Guidance) (U.S. EPA, 1989). With the
framework provided by the RI/FS Guidance and the
ground-water guidance given here, the reader should be able
to evaluate ground-water contamination at specific sites,
focusing on decisions that are pertinent to remedial actions for
contaminated ground water. The first steps in the RI/FS
process include planning how site activities will be managed
and determining data needs. Data collection occurs
throughout the RI/FS and remedy implementation process and
generally focuses on making and refining the following
decisions:
! Establishing remedial action objectives
Establishing preliminary cleanup levels
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- Determining the area of attainment
- Estimating the restoration time frame
! Developing remedial action alternatives
! Conducting a detailed analysis of the alternatives
! Selecting a remedy
! Designing and constructing the remedy
! Evaluating the remedial action performance
Figure 1-1 shows the steps comprising the Superfund RI/FS
process. Arrows from the key decision points at the bottom of
Figure 1-1 indicate where the decision points fit into the
process. Figure 1-2 provides an overview of the alternative
selection process that is specific to ground water.
1.3 Other EPA Guidance Documents
Pertinent to Ground-Water Remedial
Actions Under Superfund
Several other EPA documents provide guidance for Superfund
decision-making and may be pertinent to ground water. Table
1-1 lists these publications, describes their contents, and
notes the steps within the RI/FS process in which they will be
particularly useful.
1.4 Organization of this Document
The remainder of this document is divided into six chapters
and six appendixes, summarized below.
Chapter 2, "Statutory and Policy Framework for Ground-Water
Remedial Alternatives," discusses specific elements of the
Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA) and the written directives that have
been used to implement CERCLA and establish the policy for
ground-water remedial actions under Superfund.
Chapter 3, "Scoping Ground-Water Remedial Activities,"
describes the two planning activities conducted before data
collection: (1) planning site management activities, which
includes determining approaches for remediating ground-water
contamination i.e., identifying appropriate removal actions and
operable units; and (2) scoping data collection activities,
which involves selecting the types of ground-water studies that
will be conducted at a site.
Chapter 4, "Establishing Preliminary Cleanup Levels,"
describes how to determine preliminary cleanup levels from
available standards and health-based criteria.
Chapter 5, "Developing Remedial Alternatives," focuses on
issues specific to ground-water contamination that influence
the development of remedial action alternatives.
Chapter 6, "Detailed Analysis of Alternatives and Selection of
Remedy," discusses the alternative evaluation process and
how this process guides the selection of the final remedy.
Chapter 7, "Evaluating Performance and Modifying Remedial
Actions," addresses ground-water remedial action
performance. This section provides guidance for deciding
whether the remedial action should be continued without
modification, continued but upgraded, replaced or
discontinued because remedial action objectives have been
met and the remedy is complete.
Appendix A, "Case Study with Site Variations," presents a
hypothetical case study to demonstrate the application of the
guidance provided in this manual.
Appendix B, "Strategy for Addressing Ground-Water
Contamination From Multiple Sources Involving Superfund
Sites," presents the EPA policy framework and provides
guidance on RI/FS and remedial response activities for
multiple-source ground-water contamination sites. At these
sites, releases from sources other than the Superfund site
contribute to ground-water contamination. Ground-water
remedial actions that clean up or control releases from the
Superfund site must be combined with corrective actions for
other contaminant sources to be effective. Ground-water
remediation at these multiple-source sites may involve
coordination with agencies and authorities outside of
Superfund.
Appendix C, "Documenting an Interim Action," describes the
contents of the Record of Decision (ROD) needed to support
operable units that are taken as interim actions.
Appendix D, "Basic Ground-Water Equations," provides some
equations that can be used to estimate the restoration time
frame.
Appendix E, "Tables of U.S. EPA Standards, Criteria, and
Guidelines for, Establishing Ground-Water Cleanup Levels,"
provides a reference, current at the time of this writing, for
setting preliminary cleanup levels.
Appendix F, "Sample Letter to Obtain Property Access,"
provides a format for requesting access to adjacent properties
under which a contaminant plume has migrated.
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REMEDIAL
IHVEST16ATION
Figure 1.1 Decision Poiints in the Superfund Process,
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Characterize
Ground-Water Contamination
(Remedial Investigation)
Prepare Explanation of
Significant Differences
Does
Ground-Water
Remedy Fundamentally
Change
Revise Remedy
rogress Towards"\^ Yes
Cleanup Levels
Acceptable
Continue/upgrade
Operation; Revise
Restoration
Time Frame
Establish Preliminary Remedial
Action Objectives for Ground
Water, Including Preliminary
Cleanup Levels
Develop
Remedial Alternatives
(Feasibility Study)
Perform Detailed Analysis
of Alternatives
(Feasibility Study)
Select Remedy
(Record of Decision)
Design Remedy
Construct Remedy
Operate Remedy/
Conduct Performance Monitoring
Are
Cleanup Levels
Being Attained
Yes
r
Remedy Complete
Figure 1-2 Overview of the Ground-Water Remedy Selection Process.
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Table 1-1. EPA Guidance
Title
Alternate Concentration
Limit Guidance
Compendium of Superfund
Field Operations Methods
Data Quality Objectives for
Remedial Response
Activities (DQO Guidance)
Endangerment Assessment
Handbook
Exposure Factors
Handbook
Ground-Water Protection
Strategy
Guidance for Applicants
for State Wellhead
Protection Program
Assistance Funds Under
the Safe Drinking Water
Act
Guidance for Conducting
Remedial Investigations and
Feasibility Studies under
CERCLA
Guidance Document for
Providing Alternate Water
Supplies
Guidance on Preparing
Superfund Decision
Documents
Documents Pertinent to Ground-Water Remedial
Issuing
Office Citation Status
OSWER EPA/530-SW-87-107 Final
OERR EPA/540/P-87-001a&b Final
August 1987
OERR/OWP EPA/540/G-87/003a Final
E
OWPE U.S. EPA
August 1985 Draft
ORD U.S. EPA Draft
September 1987
OGWP U.S. EPA Final
August 1984
OGWP U.S. EPA Final
June 1987
OERR U.S. EPA Interim
March 1989 Final
OERR U.S. EPA Final
October 1987
OERR U.S. EPA Draft
March 1988
Actions Under Superfund*
Contents
Describes how to
develop alternate
concentration limits
under RCRA.
Presents techniques
used during the
fieldwork phase of the Rl
Identifies the framework
and process by which
DQOs are developed.
DQOs are qualitative
and quantitative
statements specifying
the quality of data
needed to support
Agency decisions.
Provides guidance on
conducting
endangerment
assessments.
Guidance for assessing
human exposure.
Provides framework for
protecting ground water.
Explains EPA's policies
and procedures for
implementing the
wellhead protection
assistance program.
Provides an
understanding of the
RI/FS process.
Presents structure for
conducting an RI/FS.
Provides guidance or
planning and
implementing programs
to provide alternate
water supplies.
Guidelines for
documenting and
amending Proposed
Plans and RODs.
Possible Resource for
Setting cleanup levels
for exposure-based
scenarios for Class III
ground water
Scoping and field
investigation during the
Rl
Scoping activities
Rl
Selection of exposure
assumptions and pathways
for drinking water
Scoping
Determining response
objectives
RI/FS process
Taking removal actions,
formulating remedial
alternatives
Documentation of the
selected remedy
(continued)
'Contact the EPA Public Information Center, Washington, D.C. (202) 382-2080 for information on where to obtain documents.
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Table 1-1. Continued
Title
Issuing
Office
Citation
Status
Contents
Possible Resource for
Guideline for Delineating
Wellhead Protection Area
Guidelines for Ground-Water
Classification Under the EPA
Ground-Water Protection
Strategy
Handbook for Remedial
Actions at Waste Disposal
Sites
Methods for Determining the
Locations of Abandoned
Wells
Modeling Remedial Actions
at Uncontrolled Hazardous
Waste Sites
RCRA Ground-Water
Monitoring Technical
Enforcement Guidance
Document
Superfund Exposure
Assessment Manual
OGWP EPA/440/6-87-010
OGWP U.S. EPA,
April 1988
OSW U.S. EPA,
October 1985
NWWA/EPA NWWA, 1987
OERR/ORD EPA/540/2-85-001
April 1985
OWPE
OERR
U.S. EPA, OSWER
Directive 9950.1,
September 1986
U.S. EPA, OSWER
Directive 9285.5-1,
March 22, 1988
Superfund Public Health
Evaluation Manual
OERR
EPA/540/1-86/060
(OSWER Directive
9285.1-1), October
1986
Final Describes procedures
and information needed
to specify wellhead
protection areas.
Draft Presents methods used
to classify aquifers.
Final Provides basic
understanding of
remedial actions,
describes how to select
remedial actions, and
gives an example.
Final Presents methods for
locating abandoned
wells.
Final Presents model
selection and use
guidelines for assessing
site conditions and
remedial action
performance.
Final Describes the essential
components of a RCRA
ground-water
monitoring system.
Final Provides overall
understanding of the
integrated exposure
assessment process,
references estimation
procedures and
computer modeling
techniques.
Final Provides guidance on
methods for evaluating
effects to human health.
Determining response
objectives
Classifying ground
water
Alternative
development, screening, and
evaluation
Field investigation
during the Rl
FS
Technical
considerations during
scoping and
performance evaluation
Rl (and modeling)
Rl, selecting indicator
chemicals, and
determining aggregate
effects
The CERCLA Compliance
With Other Laws Manual
Water Quality Standards
Handbook
OERR
OW/Regula-
tions and
Standards
EPA, June 1987,
OSWER Directive
9243.1-01
U.S. EPA,
December 1983
Interim Identifies potential
Final ARARS, procedures for
identifying ARARs,
waiver criteria, and
hypothetical scenarios.
Final Guidance and
implementation of
WQC.
Scoping, FS
Determination of
preliminary cleanup
levels
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Chapter 2
Statutory and Policy Framework for Ground-Water Remedial Alternatives
2.1 Introduction
This chapter identifies important provisions and requirements
of environmental statutes and policies that affect the
decision-making process at Superfund sites that have
ground-water contamination. CERCLA, as amended by the
Superfund Amendments and Reauthorization Act (SARA),
provides the statutory framework for cleaning up hazardous
waste sites, and the National Contingency Plan (NCR) (U.S.
EPA, 1985) codifies EPA's implementation policy written
under CERCLA. This chapter integrates important
requirements and provisions of both CERCLA and the policy
directives that address its implementation. Other
environmental statutes and policies that affect Superfund
ground-water remediation include:
! The Ground-Water Protection Strategy (U.S. EPA,
1984) and its associated Guidelines for
Ground-Water Classification Under the EPA
Ground-Water Protection Strategy (U.S. EPA, 1986b)
(also called Classification Guidelines) (U.S. EPA,
1986b)
! The Resource
(RCRA)
Conservation and Recovery Act
i
The Safe Drinking Water Act (SDWA)
The Clean Water Act (CWA)
Further discussion of Superfund's responsibility to meet
the environmental statutes can be found in The CERCLA
Compliance with Other Laws Manual (U.S. EPA, 1988a)
2.2 Requirements and Provisions of
CERCLA and the NCP
The proposed NCP (U.S. EPA, 1988d) incorporates the
requirements and provisions of SARA. This guidance has
been prepared on the basis of CERCLA as amended by
SARA and the existing NCP (1985) and is consistent with the
proposed NCP and directives issued by the Office of Solid
Waste and Emergency Response (OSWER) (U.S. EPA,
1986a, 1987a, and 1987k)
The following CERCLA requirements must be addressed
specifically during remedy selection and must be discussed
in the ROD. The discussion should demonstrate that the
remedy does the following:
! Protects human health and the environment
(CERCLA Section 121(b))
! Attains the applicable or relevant and appropriate
requirements (ARARs) of Federal and State laws
(CERCLA Section 121(d)(2)(A)) or warrants a waiver
under CERCLA Section 121 (d)(4)
! Reflects a cost-effective solution, taking into
consideration short- and long-term costs (CERCLA
Section 121 (a))
! Uses permanent solutions and treatment
technologies or resource recovery technologies to the
maximum extent practicable (CERCLA Section
! Satisfies the preference for remedies that
permanently and significantly reduces the mobility,
toxicity, or volume of hazardous substances as a
principal element or explains why such a remedy was
not selected (CERCLA Section 121 (b))
In addition, the following provisions of CERCLA may or may
not be pertinent to ground-water remediation depending on
site-specific circumstances:
! Alternate concentration limits (ACLs) from those
otherwise applicable or relevant and appropriate
requirements can only be used for determining off site
cleanup levels under special circumstances
(CERCLA Section 121 (d)(2)(B)(ii)).
! Ground-water remedial actions that restore ground
water are to be federally funded until cleanup levels
are achieved or up to 10 years,
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whichever comes first (CERCLA Section 104(c)(6)).
preliminary cleanup levels.
! A performance evaluation must be conducted at least
every 5 years if wastes are left onsite (CERCLA
Section 121(c)). By policy this has been interpreted
to apply where wastes are left above health-based
levels.
The requirements for a remedy to be protective and
cost-effective are discussed in detail in Chapter 6. The other
requirements and provisions and the policy for implementing
them are outlined below.
2.2.1 Applicable or Relevant and Appropriate
Requirements
When setting cleanup levels under CERCLA, ARARs are
considered in the following manner, as described in the
CERCLA Compliance With Other Laws Manual (U.S. EPA,
1988a):
! Applicable requirements are cleanup standards,
standards of control, and other substantive
environmental protection requirements, criteria, or
limitations promulgated under Federal or State law
that specifically address a hazardous substance,
pollutant, contaminant, remedial action, location, or
other circumstance at a Superfund site.
! Relevant and appropriate requirements, like
applicable requirements, are cleanup standards,
standards of control, or other substantive
environmental protection requirements, criteria, or
limitations promulgated under Federal or State law.
While not technically applicable to a hazardous
substance, pollutant or contaminant, remedial action,
location, or other circumstance at a Superfund site,
relevant and appropriate requirements address
problems or situations sufficiently similar to those
encountered at a Superfund site so that their use is
well-suited.
Policies for determining which requirements at a site are
ARARs have been described in guidance documents (U.S.
EPA, 1988a and 1987k). Figure 2-1 presents several
action-specific ARARs that may be required for various
ground-water remedial actions. ARARs typically fall into three
categories:
! Chemical-specific ARARs are health- or
environmentally based numerical values limiting the
amount of a contaminant that may be discharged to,
or allowed to remain in, environmental media. These
include, for example, maximum contaminant levels
(MCLs) established under the SDWA. Generally,
chemical-specific ARARs are used when setting
! Location-specific ARARs restrict activities of limit
concentrations of contaminants in effluent because a
site is in a special location such as a floodplain,
wetland, or historical area.
! Action-specific ARARs are technology- or activity-
based limitations and may include, for example,
limitations of discharges of treated water to streams.
ARARs most pertinent to ground-water remedies relate to
setting cleanup levels, operating treatment processes, and
managing treatment residuals. CERCLA specifies six
conditions under which ARARs may be waived (CERCLA
Section 121(d)(4)). These are discussed in Chapter 6.
2.2.2 Use of Permanent Solutions and
Treatment Technologies to the Maximum
Extent Practicable
CERCLA requires an assessment of permanent solutions and
treatment technologies and mandates that they be used to
the maximum extent practicable. Information on treatment
technologies suitable to ground water is presented in Chapter
5.
The additional cost and time associated with treatability
testing and uncertainties associated with implementing a
technology that is not in common use should be considered
when assessing treatment. The practicable extent to which
permanent solutions and treatment technologies can be used
is based on a site-specific analysis of alternatives against
nine evaluation criteria.
2.2.3 Preference for Treatment as a Principal
Element
CERCLA expresses a preference for remedies that employ
treatment that permanently and significantly reduces the
mobility, toxicity, or volume of hazardous substances as a
principal element. Emphasis is placed on destruction or
detoxification of hazardous materials rather than on protection
strictly through prevention of exposure. Furthermore, the
statute requires an explanation of why this preference is not
met when the principal threats are not treated. This is
discussed further in Chapter 6.
2.2.4 CERCLA Restrictions on Establishing
ACLs
CERCLA specifies that ACLs, (i.e., levels of contamination
that will remain in the ground water at the completion of the
remedial action that are above levels safe to human health and
the environment but to which exposure is prevented) cannot
be
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Contaminated
Ground Water
No or
Limited Action
Natural
Attenuation
Pump
and Treat
Containment/
Gradient Control
In Situ
Treatment
ARARs:
RCRA Subpart F
Corrective Action
Requirements
. MCLs
ARARs:
RCRA Subpart F
Corrective Action
Requirements
MCLs
Stream
CERCLA
Section 121 (d)(2)(B)(ii)
ARARs:
RCRA Subpart F
Corrective Action
Requirements
MCLs
ARARs:
RCRA Subpart F
Corrective Action
Requirements
ARARs:
RCRA Subpart F
Corrective Action
Requirements
MCLs
>
f >
Residual
Gases
1 \
Treated
Groundwater
f
Residual
Solids
ARARs:
State Air Toxics
Regulations
NESHAP
ARARs:
Land Disposal
Restrictions
>
r
Reinjectfon
\
f
Distribution System
\
r
POTW
>
r
Surface Water
ARARs:
MCLs
ARARs:
Pretreatment
Regulations
ARARs:
Substantive Require-
ments of NPDES
(onsite)
Figure 2.1 Possible Action-Specific ARARs for Ground-Water Remedial Actions.
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established for ground water if the process for remedial
establishing the ACLs assumes that the first point of and
human exposure is beyond the boundary of the evaluations
facility, except under the following scenario: The ground water
has a known or projected point of entry to surface water and
there are no statistically significant increases in contaminant
concentration in the surface water or at any point at which
contaminants are expected to accumulate. In addition, there
must be reliable institutional controls preventing exposure to
ground-water contaminants that are above cleanup levels. It is
the policy of EPA that this provision be used only when
cleanup to ARARs is not practicable. The method for
establishing ACLs under CERCLA generally considers the
factors specified for water establishing ACLs under RCRA,
but, for the most part, will be governed by the restrictions
outlined above. This is discussed further in Chapter 4.
2.2.5 Funding Remedial Actions
Funds for remedial activities come from both Federal and
State sources unless enforcement actions have provided for
potentially responsible party (PRP)-led investigation or
remediation (i.e., cases for which cost recovery is planned or
there are viable PRPs). States are required to pay up to 10
percent of the costs of the remedial action. Federal funding
of remedial actions that restore ground or surface water
continues for up to 10 years. After 10 years or when cleanup
levels are achieved, the State fully funds any necessary
operation and maintenance. The 10-year funding provision
should be applied only to actions to restore ground or surface
waters and not to actions to reduce exposure to
contaminants. For example, if ground water is pumped and
treated to provide an alternate water supply and not to restore
the ground water, this provision should not be applied, and
Federal funding would only cover capital and startup costs.
Also, Federal funding would not cover long-term leachate
control actions, i.e., actions in which leachate is extracted
and treated as part of the source control remedy. If the facility
responsible for the contamination is operated by a state or a
political subdivision of a state, the state is required to pay 50
percent of the cost of the remedial action (CERCLA Section
104(f)). Additional information on funding remedial actions is
available from "Interim Guidance on Funding for Ground and
Surface Water Restoration" (U.S. EPA, 1987e).
2.2.6 Evaluating Remedial Action Performance
CERCLA requires that remedial actions be reviewed and
periodically and at least every 5 years after initiation of the
remedial action as long as contaminants remain at the site.
For ground-water remediation, performance evaluations (or
5-year reviews) are required as long as contaminant
concentrations exceed health-based levels. Performance
evaluations are routinely conducted throughout a
remedial action at a frequency that is site-specific and usually
involve annual monitoring. Performance evaluations are
discussed further in Chapter 7.
2.3 U.S. EPA's Ground-Water
Protection Strategy and
Classification Guidelines
It is the policy of EPA's Superfund program to use as a guide
the framework provided by EPA's Ground-Water Protection
Strategy (U.S. EPA, 1984) in determining the appropriate
remediation for contaminated ground water. Three classes of
ground water have been established on the basis of ground-
water value and vulnerability to contamination. The
Classification Guidelines (U.S. EPA, 1986b) provides
guidance in determining the potential beneficial uses of the
contaminated ground water, i.e., whether it is Class I, Class
II, or Class III. The expected use of the Ground-Water
Protection Strategy and Classification Guidelines is described
in the forthcoming policy statement entitled "Implementation
of Ground-Water Classification in the Environmental
Protection Agency."
The various ground-water classes are described nest.
Special ground water (Class I) is (1) highly vulnerable to
contamination because of the hydrological characteristics of
the areas in which it occurs, and (2) characterized by either
of the following factors:
! The ground water is irreplaceable; no reasonable
alternative source of drinking water is available to
substantial populations.
! The ground water is ecologically vital; the aquifer
provides the base flow for a particularly sensitive
ecological system that, if polluted, would destroy a
unique habitat.
Current and potential sources of drinking water and water
having other beneficial uses includes all other ground water
that is currently used (IIA) or is potentially available (MB) for
drinking water, agriculture, or other beneficial use.
Ground water not considered a potential source of drinking
water and of limited beneficial use (Class IMA and Class NIB)
is saline, i.e., it has a total dissolved solids levels over 10,000
milligrams per liter (mg/l), or is otherwise contaminated by
naturally occurring constituents or human activity that is not
associated with a particular waste disposal activity or another
site beyond levels that allow remediation using methods
reasonably employed in public water treatment systems.
Class III also includes ground water that is
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not available in sufficient quantity at any depth to meet the
needs of an average household.
Class MIA includes ground water that is interconnected to
surface water or adjacent ground water that potentially could
be used for drinking water. Class 1MB includes ground water
that has no interconnection to surface water or adjacent
aquifers. For Class IMA ground water, establishing cleanup
levels should take into consideration the degree of
interconnection to Class I or Class II ground water or the rate
of discharge to surface water so that levels of contaminants in
higher class ground water do not increase as a result of the
interconnection.
According to the Classification Guidelines, the Class III
designation may apply to ground-water contamination that is
caused by human activity and is widespread and not
attributable to a specific site. For the Superfund process,
however, remedial action objectives for Class III ground water
that is contaminated as a result of human activity would
typically be determined initially using the process described
in this guidance for Class II ground water and may involve
coordination with other parties, as described in Appendix B.
This is further described in Chapter 4.
Using the Classification Guidelines as a guide, a
determination is made as to whether ground water falls within
Class I, Class II, or Class III. The specifications for the three
classes are outlined in Figure 2-2. Such classifications are
site-specific and limited in scope. Ground water is classified
by EPA under the Superfund program to assist in determining
the appropriate type of remediation for a Superfund site.
Classifications performed by EPA under the Superfund
program do not apply to the general geographic area in which
they are performed, nor to any Federal, State, or private action
other than Superfund remediation.
Some states have developed and promulgated their own
ground-water classification systems. A State's classification
system may be used to determine remediation goals.
Furthermore, a promulgated State system may be an ARAR.
In addition, State wellhead protection programs, especially
those developed pursuant to the SDWA, may influence
classification of ground water (U.S. EPA, 1987g). For
example, if a Superfund site is within a wellhead protection
area, Class IIA ground water may be treated as Class I. The
Guidance for Applicants for State Wellhead Protection
Program Assistance Funds Under the Safe Drinking Water
Act (1987e) describes the criteria for establishing wellhead
protection areas.
2.4 Application ofRCRA to Ground-
Water Remediation
Pertinent RCRA regulations are presented in this section to
familiarize the reader with its provisions.
Throughout this discussion, RCRA's relationship to Superfund
remediation is discussed. RCRA requirements that potentially
are applicable or relevant and appropriate to Superfund
ground-water actions include the land disposal restrictions (40
CFR 268) and the ground-water monitoring and response
program (40 CFR 264, Subpart F). Regulations for corrective
action at solid waste management units (40 CFR 264,
Subpart S), referred to here al the subpart S regulations, are
being developed and may also be applicable or relevant and
appropriate when promulgated. RCRA requirements regarding
closure of units may also be ARARs at Superfund sites at the
completion of remedial action. Because the closure
requirements that address ground-water contamination refer
simply to Subpart F, closure specifications will not be
addressed as a separate section in this guidance.
2.4.1 The Land Disposal Restrictions
The RCRA land disposal restrictions require that hazardous
waste be treated to established levels before being placed in
a land-based unit. The schedule for implementation of the land
disposal restrictions is presented in Table 2-1.
Ground-water treatment residuals from Superfund remedial
actions, such as spent carbon or ion exchange resins that are
contaminated with RCRA-listed waste for which treatment
standards have been promulgated must either meet the land
disposal restrictions or be delisted under RCRA before
disposal. Ground-water treatment system residuals from
Superfund remedial actions that exhibit the RCRA-hazardous
waste toxicity characteristic will have to be treated until
concentrations are below the characteristic levels established
under RCRA before disposal once the land disposal
restrictions for characteristic wastes become effective.
Treated ground water from Superfund remedial actions that is
discharged to surface water must meet the substantive
requirements of a National Pollutant Discharge and
Elimination System (NPDES) permit but would not have to
meet the RCRA land disposal restriction levels, because
discharges to surface waters that meet the requirements of an
NPDES permit are exempt from the RCRA land disposal
restrictions.
Treated ground water that is discharged to a publicly owned
treatment works (POTW) must meet the pretreatment
requirements of the POTW, as specified by the CWA. If the
discharge will go to a POTW that does not have established
pretreatment standards, the remedial action should be
evaluated to determine if the POTWs NPDES permit will be
in violation as a result of the discharge. The land disposal
restrictions are only triggered when the treated ground water
is placed directly in a surface impoundment.
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CUSS I GROUND WATER
CUSS I! GROUND WATER
CUSS III GROUND WATER
'Presumed it unknown
Figure 2-2 Ground-Water Classification Row Chart.
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Table 2-1. Schedule for Implementation of the Land Disposal Restrictions
Wastes
Effective Date of Ban
Solvents and Dioxin
Wastes3
California List Wastesb
Remaining Wastes0
F001 to F005 (Spent solvents)
F020 to F023, F026 to F028 (Dioxin-containing wastes)
Soil and debris contaminated with certain solvents and dioxins from
CERCLA/RCRA corrective actions
Soil and debris contaminated with certain solvents and dioxins not from
CERCLA/RCRA corrective actions
Solvent wastes from small quantity generators
Solvent wastes generated from CERCLA/RCRA corrective actions
Solvent-water mixtures, solvent-containing sludges and solids, and non-
CERCLA/RCRA corrective action soil with less than 1 percent total solvent constituents
California list (except HOCs)
Dilute HOCs (Greater than or equal to 1,000 mg/l and less than 10,000 mg/l)
Liquid and non-liquid HOCs
Soil and debris contaminated with HOCs not from CERCLA/RCRA sites
Soil and debris contaminated with HOCs from CERCLA/RCRA corrective actions
One-third of all ranked and listed hazardous waste ("First Third") except:
Petroleum Refining Wastes (K048, K049, K050, K051, K052)
Electric Arc Furnace Dust (K0621~high zinc)
Brine Refining Muds/Mercury Cell Process (K071)
Wastewater Treatment Sludge/Mercury Cell Process (K106)
Soil and debris contaminated with First Third Wastes for which BOAT is
solids incineration
Novembers, 1986
Novembers, 1988
Novembers, 1990
Novembers, 1988
Novembers, 1988
Novembers, 1988
Novembers, 1988
JulyS, 1987
JulyS, 1987
Novembers, 1988
JulyS, 1989
Novembers, 1990
Augusts, 1988
Augusts, 1990
Augusts, 1990
Augusts, 1990
Augusts, 1990
Augusts, 1990
Two-thirds of all ranked and listed hazardous wastes ("Second Third")
All remaining ranked and listed hazardous wastes and all hazardous wastes
identified by characteristic under RCRA Section 3001 ("Third Third")
Any hazardous waste listed or identified under RCRA Section 3001 after
Novembers, 1984
JuneS, 1989
MayS, 1990
Within 6 months of the
date of identification or
listing
aThe solvent and dioxin wastes are:
F001 Spent halogenated solvents used in degreasing (e.g., tetrachloroethylene, trichloroethylene, methylene chloride)
and sludges from the recovery of these solvents in degreasing operations.
F002 Spent halogenated solvents (e.g., tetrachloroethylene, trichloroethylene, methylene chloride) and still bottoms from the recovery of
these solvents.
F003 to F005 Spent non-halogentated solvents (e.g., xylene, acetone, cresols, toluene, methyl ethyl ketone) and still bottoms from the
recovery of these solvents.
F020 to F023 and F026 to F028 Dioxin-containing wastes
The California lists wastes are RCRA-listed hazardous wastes that are liquids except halogenated organic compounds (HOCs), and
! Contain free cyanides (greater than or equal to 1,000 mg/l)
! Contain PCBs (greater than or equal to 50 ppm)
! Contain HOCs (greater than or equal to 1,000 mg/kg)
! Have a pH less than 2
! Contain certain metals:
-Arsenic (greater than or equal to 500 mg/l)
-Cadium (greater than or equal to 100 mg/l)
-Chromium (greater than or equal to 500 mg/l)
-Lead (greater than or equal to 500 mg/l)
-Mercury (greater than or equal to 20 mg/l)
-Nickel (greater than or equal to 134 mg/l)
-Selenium (greater than or equal to 100 mg/l)
-Thallium (greater than or equal to 130 mg/l)
cSee 40 CFR 268.10.
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Discharges via the sewage system are exempt from the land
disposal restrictions under the domestic sewage exemption.
2.4.2 The RCRA Ground-Water Monitoring and
Response Program
The RCRA ground-water protection standards establish
requirements for regulated units (surface impoundments,
waste piles, land treatment units, and landfills) that received
hazardous waste after July 26, 1982. Because most
Superfund sites have not received hazardous waste since this
date, the RCRA ground-water regulations generally are not
applicable to Superfund sites unless the Superfund action
involves active placement of RCRA wastes in such units.
However, these requirements may be relevant and appropriate.
RCRA requirements are generally met by standard procedures
used for Superfund sites, and RODs should contain language
to this effect. Feasibility studies and RODs need only note
this consistency in the ARAR discussions. RCRA regulations
specify monitoring requirements, concentration standards,
and corrective action measures. These are described in the
following paragraphs.
2.4.2.1 Monitoring Requirements
The RCRA monitoring requirements consist of three,
categories: detection monitoring, compliance monitoring, and
corrective action monitoring.
! Detection monitoring is used to determine if a release
to ground water has occurred.
! When a release has occurred, compliance monitoring
is used to determine if any ground-water
concentration standards have been exceeded.
! Corrective action monitoring is used when the
ground-water protection standard has been exceeded
and corrective action is implemented. Corrective
action monitoring establishes the effectiveness of
measures taken to remediate ground water.
At a Superfund site with contaminated ground water, it has
already been determined that a ground-water remediation
decision must be made. Therefore, RCRA's detection
monitoring and compliance monitoring requirements are not
generally relevant and appropriate. However, RCRA corrective
action monitoring requirements may be applicable or relevant
and appropriate. If a new hazardous waste treatment storage
or disposal facility is created as a result of remedial actions
taken at the site, detection and compliance monitoring may
also be applicable.
2.4.2.2 Concentration Standard
Concentration standards under the RCRA ground-water
protection standards (Subpart F) are the background level of
the constituent, the MCL for the constituent (RCRA MCL), or
an alternate concentration limit (RCRA ACL). (RCRA MCLs
have been so noted because currently there are no automatic
provisions for revising or supplementing the MCLs in RCRA as
they are promulgated or revised under the SDWA.) As
discussed in Chapter 4 of this guidance, Superfund ground-
water remedies for existing or potential sources of drinking
water should reduce concentrations to existing MCLs or to
more stringent State standards. Contaminants for which
MCLs have not been set must meet cleanup levels derived
from other health-based or environmentally based standards,
a process that is comparable to using RCRA ACLs derived
from health-based considerations. Therefore, Superfund is
generally consistent with the requirements of RCRA. This
should be noted in the ROD.
For Class III ground water, it is expected that both RCRA and
Superfund would require similar cleanup approaches
considering the factors listed under the RCRA regulation's
ACL provision (e.g., physical and chemical characteristics of
the waste, including its potential for migration, current and
future uses of the ground water, and the existing quality of
ground water) since this is a determination based on
exposure. Additional information on RCRA's ACL provision is
available in the Alternate Concentration Limit Guidance (U.S.
EPA, 1987b.)
2.4.2.3 Corrective Action Program
Under RCRA, a corrective action program is implemented if a
release above the ground-water protection standard is
confirmed. The corrective measures under RCRA include
removal or treatment in place of any hazardous constituents
that exceed RCRA's established concentration limits. These
action-specific measures may be applicable or relevant and
appropriate requirements for Superfund. They are summarized
below and discussed in conjunction with Superfund
requirements.
! RCRA requires a corrective action program that
prevents hazardous constituents from exceeding
concentration limits at the compliance pointthe
boundary of the waste management areaif any
concentration level exceeds the ground-water
protection standard. Consistent with statutory
mandates, the Superfund cleanup goal, on the other
hand, is to attain health-based standards within the
area of attainment-the area that encompasses the
entire contaminant plume beyond the boundaries
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of any waste managed in place as part of the final
remedy. Therefore, the area of the plume to be
remediated under Superfund is consistent with the
area of the plume to be remediated under RCRA.
! In addition to requiring a corrective action program,
RCRA requires that a ground-water monitoring
program be implemented to demonstrate the
effectiveness of the corrective action. RCRA
corrective action measures may be terminated when
ground-water monitoring data demonstrate that the
contaminant levels are below the ground-water
protection standard for a period of 3 years. (EPA is
reevaluating this 3-year requirement and anticipates
making the time period site specific.) Under
Superfund, requirements for evaluating the
effectiveness of a remedy are site-specific and must
demonstrate that cleanup levels are achieved. This is
generally consistent with the RCRA requirements.
2.4.3 The Subpart S Regulations
Under Subpart S of the RCRA regulations, requirements for
corrective action at solid waste management units (SWMUs)
are currently being drafted. The basic requirements for SWMU
corrective action are currently in effect under the authority of
the Hazardous and Solid Waste Amendments of 1984.
SWMUs include both regulated and previously unregulated
units at RCRA facilities without regard to the time the waste
was received. Subpart F, discussed above, is also being
revised to ensure consistency between Subpart F and Subpart
S.
Subpart S will cover all releases to soil, air, and surface water
and some releases to ground water from SWMUs. The
releases to ground water that Subpart S will cover include (1)
releases to ground water from regulated units if treatment,
storage, disposal occurred before July 26, 1982, and (2)
releases from unregulated units (i.e., those not regulated
under Subpart F) without regard to the time of activity. When
these regulations are promulgated they may be applicable or
relevant and appropriate to Superfund sites.
Remediation of ground-water releases from regulated units
receiving waste after July 26, 1982, will still be covered under
Subpart F.
2.5 The Safe Drinking Water Act
Three provisions of the SDWA may pertain to Superfund
ground-water remediation: the drinking water standards, the
underground injection control (UIC) program, and the State
wellhead protection program.
MCLs developed under the SDWA generally are ARARs for
current or potential drinking water sources within the area of
attainment. Although MCLs are developed using cost and
technical considerations, they are also protective of human
health for exposure from drinking water. There are currently 38
promulgated primary MCLs for chemicals. Eighty-three MCLs
will have been promulgated by 1989, 25 additional MCLs are
to be proposed by 1991, and an additional 25 MCLs are to be
proposed every 3 years thereafter. For Superfund, cleanup
levels that are more stringent than MCLs may be required to
achieve adequate protection in some cases; these are
discussed in Chapter 4.
EPA has also developed MCL goals (MCLGs) that are entirely
health based. MCLGs serve as guidance for establishing
MCLs. Under Superfund, MCLGs may be considered when
setting cleanup levels in situations where multiple pathways
or multiple contaminants increase risks, as discussed in
Chapter 4.
The UIC program developed under the SDWA provides
standards and procedures for underground injection of fluids.
Underground injection wells are divided into the following five
general classes for permitting and regulatory purposes:
! Class I wells are those used to inject industrial,
hazardous, and municipal wastes beneath the lower
most formation containing an underground drinking
water source within 1/4-mile of the well bore.
! Class II wells are those used to dispose of fluids that
are brought to the surface in connection with oil and
gas production, to inject fluids for the enhanced
recovery of oil or gas, or to store liquid hydrocarbons.
! Class III wells are those used to inject fluids for the
extraction of minerals.
! Class IV wells are used to inject hazardous or
radioactive waste into or above a formation that
contains an underground drinking water source that
is within 1/4-mile of the well. Operation or
construction of Class IV wells, though generally
prohibited, is allowed as part of a Superfund remedial
action if the wells are used to reinject treated ground
water into the same formation from which it was
withdrawn.
! Class V wells include all wells not incorporated in
Classes I through IV, including, for example, recharge
wells, septic system wells, and shallow industrial
disposal wells.
Superfund ground-water actions would most likely involve
Class IV wells. There are currently no substantive
requirements in the regulations for the construction of these
wells; closure of Class IV wells (40 CFR 144.23) requires only
that the well be
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plugged or closed in a way that is acceptable to the Regional
Administrator.
According to the SDWA's State wellhead protection program,
states are required to develop programs to establish wellhead
protection areas to protect public water supply systems from
contamination. These programs may be location-specific
ARARs for Superfund remedial actions and under certain
circumstances may lead to a higher level of cleanup at sites
within wellhead protection areas, according to the State
wellhead protection program. Additional guidance on the
wellhead protection programs can be found in Guidelines for
Delineation of Wellhead Protection Areas (U.S. EPA, 1987g)
and the Guidance for Applicants for State Wellhead
Protection Program Assistance Funds Under the Safe
Drinking Water Act (1987e).
2.6 The Clean Water Act
The CWA establishes permit requirements and discharge
limits for remedial actions that involve the discharge of treated
or untreated contaminated ground water into a navigable
stream. Provisions of the CWA that may be ARARs include
the following:
! Regulation of discharges to surface waters through
the NPDES permitting process
! Best available technology (BAT) and best
conventional technology (BCT) for treating
wastewaters
! Water quality criteria (WQC) (U.S. EPA, 1986d),
which are discussed further in Chapter 4
! Water quality standards that must be promulgated by
states
NPDES Discharges to Surface Water. Both onsite and offsite
discharges from CERCLA sites to surface water are required
to meet the substantive NPDES requirements. In addition,
offsite discharges are required to meet the administrative
requirements.
Best Available Technology and Best Conventional
Technology. All direct discharges to surface water must meet
technology-based guidelines. For toxic and nonconventional
pollutants, the BAT that is economically achievable must be
used, while for conventional pollutants, the BCT must be
used. At CERCLA sites, BAT and BCT are determined on a
case- by-case basis using Best Professional Judgment. Once
the technology is selected, the numerical effluent discharge
limits are derived by applying the levels of performance of the
treatment technology to the wastewater discharge. The
numerical effluent limits must be consistent with the State's
water quality standards.
Water Quality Criteria. WQC for protection of human health
and aquatic life are established by EPA and serve as
guidelines to states, which are required to set water quality
standards for use in implementing their NPDES permitting
programs.
Water Quality Standards. Water quality standards are
numerical limitations that must be met in the receiving water
body at all times. Thus, the dilution of the effluent in the
receiving water body must be determined. Discharges of
wastewater at CERCLA sites must be consistent with these
promulgated standards.
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Chapter 3
Scoping Ground-Water Remedial Activities
3.1 Introduction
Before collecting any data, it is useful to conduct two planning
activities:
! Site management planning, which involves
identification of the types of actions that are taken to
address site problems and their optimal sequence
! Project planning, which includes such activities as
scoping data collection activities and initiating
identification of ARARs
Figure 3-1 illustrates the planning process for ground-water
remedial alternatives. This chapter will concentrate on site
management planning and scoping. These two tasks will be
discussed in terms of implementing remedial actions at sites
with ground-water contamination. Assistance and advice in
conducting ground-water investigations can be obtained from
EPA laboratory resources-specifically the Environmental
Monitoring Systems Laboratory (Las Vegas, Nevada) for
monitoring and site characterization assistance and the
Robert S. Kerr Environmental Research Laboratory (Ada,
Oklahoma) for fate and transport evaluations. In addition, other
Federal agencies, including the U.S. Geological Survey, U.S.
Army Corps of Engineers, Department of Interior, and the
Agency for Toxic Substances and Disease Registry, can also
provide assistance.
3.2 Site Management Planning
During site management planning, existing data are evaluated
and a conceptual understanding of the site is developed. This
conceptual understanding should incorporate all known and
suspected sources of contamination, types of contaminants
and affected media, routes of migration, and human and
environmental receptors. Site management planning is refined
as data are collected and the site characteristics and
contaminant migration pathways are better understood.
Site management planning identifies the response approaches
that will be taken to address the site
problems. Two response approaches can be taken to
remediate ground water at Superfund sites:
! Removal actions can be taken to prevent human
exposure to contaminants that may cause health
effects and to prevent further degradation of the
ground water.
! Remedial actions can be taken as operable units.
Operable units are (1) final actions that completely
address a discrete area of a site or (2) interim actions
taken to mitigate a threat or prevent further
degradation of ground water.
3.2.7 Removal Actions
Removal actions are authorized for any release that presents
a threat to public health, welfare, or the environment, as
determined by the lead agency (U.S. EPA, 1987J). CERCLA
limits Superfund-financed removal actions to $2 million and 12
months unless the criteria for granting an exemption to the
statutory limits are satisfied.
In addressing ground-water contamination problems, removal
actions may be used in several ways: (1) to provide alternate
water supplies, (2) to prevent plume migration by
implementing methods such as barrier wells and interceptor
trenches, (3) to pump and treat contaminated ground water,
or (4) to control the source of contamination (e.g., by
excavating soil hot spots or buried drums). In determining
whether to use removal authority, the lead agency considers
the nature of the threat, the scope of the response, and the
availability of other response mechanisms. Furthermore, if a
removal action will be used for (1), (2), or (3) above, it must be
shown that an existing drinking water supply is threatened
and that the removal program action level policy is satisfied.
The Office of Emergency and Remedial Response (OERR)
action level policy1, discussed in greater detail in Section
3.2.1.1, states that removal actions
1The action level referred to here is not the same as the action level that
triggers corrective action discussed in the RCRA regulations.
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SITE MANAGEMENT
PLANNING
Collect Existing
Site Data
Develop Conceptual
Understanding of the Site
- Nature & Extent of
Contamination
- Exposure Pathways
Execute Limited
Studies
Is
Limited
Field Investigation
Needed
Yes
Plan Limited
Studies
Develop Site
Management
Strategy
Implement Any
Removal Actions
'^vffr. ty/vj
,,, w
>? X ^
^AJ-.
*
Initiate Discussion of
Contaminant-Specific
ARARs for
Ground Water
Figure 3-1 Planning and Scoping Ground-Water Remedial Activites.
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may be implemented if (1) the numeric action levels
established by OERR are exceeded at the drinking water tap,
or (2) a site-specific health effects analysis is conducted, and
the analysis indicates that the site poses a serious health
threat. Figure 3-2 indicates the steps under the removal action
level policy for determining if a removal action should be
implemented in these cases.
In general, removal actions are most useful for providing
alternate water supplies and source control actions.
Ground-water plume control and treatment is outside the
scope of removal authority for many sites because of the
$2-million/12-month statutory limits on removal actions.
However, there are two types of statutory exemptions
available to these limits: (1) the emergency exemption, and
(2) the consistency exemption. Under the OERR action level
policy, to qualify for an emergency exemption, the exemption
request must demonstrate that contaminant levels exceed the
10-day health advisory, significantly exceed the numeric
action levels, or that an emergency exists based on site-
specific factors. If contaminant levels exceed the numeric
action level by only a minimal amount, a consistency
exemption may be warranted. The Superfund Removal
Procedures manual (U.S. EPA, 1988f) provides more
information on preparing an exemption request. States and
PRPs should be encouraged to pursue removal actions,
particularly provision of alternate water supplies as described
in the "Removal Program Priorities" memorandum (U.S. EPA,
1988e).
For any site at which a removal action is being considered,
the remedial project manager (RPM) should consult the
regional removal program office to ensure that removal
authorities and procedures are correctly understood. Although
an RI/FS and a Record of Decision (ROD) are not required for
removal actions, an Action Memorandum must be prepared for
all removals, and engineering evaluation/cost analysis is
required for certain removal actions.
3.2.1.1 Action Levels for Undertaking
Removal Actions
Action levels to determine whether a removal action should be
implemented in response to ground-water contamination have
been established by OERR (U.S. EPA, 1987J). Action levels
may be either: (1) numeric values based on drinking water
equivalent levels (DWELs) and, for potential human
carcinogens, the 10~4 excess lifetime cancer risk level, or (2)
site-specific factors (see Chapter 4 for a discussion of
DWELs). Sites may qualify for removal action if the numeric
trigger is exceeded at the drinking water tap, or an analysis of
site-specific factors has been performed that indicates that a
significant health threat exists. Exhibit 3-1 presents an
example of a removal action taken because action levels were
exceeded. Removal actions to prevent future health threats
may also be undertaken if it can be demonstrated that a
numeric action level will be exceeded within 6 months.
Action Levels Based on Numeric Values. Numeric action
levels for providing removal actions at Superfund sites are
summarized below:
Carcinogens
Volatiles
Lower of (50% x
DWEL) and
10"4 excess
lifetime cancer
risk
Noncarcinogens 50% x DWEL
Non-volatiles
Lower of DWEL
and 10"4 excess
lifetime cancer
risk
DWEL
Exceptions to Numeric Action Levels. Numeric action levels
should not be used for certain contaminants. The ERD of
OERR will develop an action level on a site-specific basis for
two situations:
! The calculated action level fora contaminant is lower
than or equal to the MCL, e.g., vinyl chloride.
! The calculated action level is based on the DWEL,
but the 10-day health advisory is lower than the
DWEL, e.g., barium. Removal actions may be
undertaken if the concentrations of these
contaminants exceed the DWEL. If the concentration
is between the DWEL and the 10-day health advisory,
ERD will review individual site conditions.
Action Levels Based on Site-Specific Factors. Removal
actions may be undertaken on the basis of site-specific
factors if a significant health threat exists, even though the
numeric action level has not been exceeded. Under these
circumstances, the health risks posed at the site must be
analyzed in detail, and the analysis must indicate that site-
specific factors result in a serious health threat.
ERD approval must be obtained before initiating any removal
action an the basis of site-specific factors unless an
emergency exists, in which case ERD must be notified as
soon as possible.
3.2.1.2 Source Control
Removal actions can also be used to excavate hot spots such
as buried drums in soil and other contaminant sources. These
actions prevent or reduce further ground-water degradation.
Actions to remove surface and subsurface contamination do
not have to satisfy the removal action level policy, although
the Action Memorandum for the site must
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Exhibit 3-1. Removal Action at the Cherokee Site
The ground water throughout a major portion of Cherokee County, Kansas, is contaminated with metals as a result of past
mining practices. Because soil contamination is very extensive, a source control action is not feasible. Remedial actions
at the site are being considered for the overall region.
Eight residences were found to have levels of cadmium in their drinking water above its action level of 17 ug/l, which is the
DWEL.
Upon evaluation of these data, the regional office determined that a removal action should be implemented. In-line
filtration/ion exchange systems were provided to reduce or eliminated toxic metal exposure to the eight families using the
contaminated welts. Water samples were taken from the homes with the treatment systems to ensure that the families were
being protected.
show that a threat to human health or the environment exists.
3.2.2 Operable Units
Operable units are portions of an overall response action that
by itself eliminates or mitigates a release, a threat of a
release, or an exposure pathway. An operable unit may reflect
the final remediation of a defined portion of a site. Chapters 5
and 6 provide detailed discussions of the process for defining
operable units and evaluating them to provide a basis for
selecting a remedy. Examples of operable units related to
ground water include:
! Providing an alternate water supply
! Remediating a contaminant plume
! Remediating hot spots
! Remediating contamination in a shallow aquifer
! Remediating contamination in a deep aquifer
Source control actions are sometimes also implemented as
operable units. Ground-water remedial actions cannot be
evaluated without considering source control actions, because
source control actions generally contribute to ground-water
restoration. Cleanup levels for soil should protect ground water
if there is a potential for migration to ground water. A
ground-water action implemented before a source control
action is selected should be based on an analysis of a range
of source control actions and their effects on ground-water
remediation. Exhibit 3-2 is an example of a site with several
operable units.
The following factors can help to identify potential operable
units.
! Presence and location of hot spots-Can a remedial
action be implemented to reduce or eliminate hot
spots without adversely affecting the overall plume?
! Site geology, including hydrogeology and
stratigraphy-Can one zone of contamination be
remediated while investigation of other zones of
contamination continues, or are the zones too closely
interconnected?
! Chemical and physical nature of contaminants as it
affects their removal-Are some contaminants
amenable to air-stripping, for example, while others
are amenable to gradient control?
! Extent and location of threats to human health and
the environment-^ action needed to alleviate a
potential threat while the investigation continues?
At many sites, it is appropriate to implement an operable unit
as an interim action before completing the RI/FS. Operable
units taken as interim actions should eliminate, reduce, or
control human health risk; be consistent with the final remedy;
and satisfy the statutory requirements described in Chapter 2.
They are generally followed by subsequent remediation.
Ground-water interim actions include source control actions
that prevent further ground-water degradation, provision of
alternate water supplies, and pump and treat actions. One
important advantage of interim actions is that they facilitate
the collection of valuable data that will reduce uncertainty at
the site and lead to more effective final remedies. When
appropriate, interim actions should be flexible and should
provide for contingency measures that are consistent with
information obtained during implementation. Documentation of
interim actions is described in Appendix C.
Interim actions may be implemented to prevent exposure to
contaminants or prevent further degradation of ground water
(by remediating hot spots, for example). This is discussed in
the following sections.
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Sample Drinking
Water Wells
Does Any
"Contaminant Exceec
Its Action Level or Will
Any Action Level Be
Exceeded within
BMonths?,
,Yes
No
Conduct a Site-Specific
Health Effects Assessment
Implement
a Removal Action if the
Site Otherwise Qualifies
for Response
Does
Any Contaminant
Pose a Serious
Health Threat
Does
Any Emergency
Exist
Removal is
not Justified
Obtain Approval
from Emergency
Response
Division (ERD)
Implement Removal Action
if Site Otherwise Qualifies
for Response; Notify
ERD as Soon as Possible
Figure 3-2 Removal Action Level Policy Flow Chart.
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Exhibit 3-2. Identifying Operable Units
The Combe Fill South Landfill, New Jersey, is an inactive municipal landfill consisting of three separate fill areas covering about 65
acres. Because it is situated on a hill, surface water drains almost radially from the site. Leachate runoff, ground water, and
surface-water runoff from the southern portion of the site constitute the headwaters of Trout Brook, which flows southeast toward
a river.
Natural unconsolidated deposits of local soils and granitic saprolite overlie highly fractured granite bedrock. A shallow aquifer lies
in the saprolite layer, saturating much of the waste, with a deeper aquifer in the fractured bedrock. The deep aquifer is the major
source of potable water in the vicinity of the landfill. Numerous residential wells draw waterfrom this aquifer, and a municipal well
is about 1 mile from the site. In localized areas, the shallow aquifer is able to provide domestic water supplies.
The landfill was originally approved by the state for disposal of municipal and nonhazardous industrial wastes, sewage sludge,
septic tank wastes, and waste oils. Approximately 5 million cubic yards of waste material are buried at the landfill.
The Rl performed at the site revealed the presence of a wide range of contaminants, consistent with the known uses of the site
and the variety of wastes accepted there. The Rl produced three major findings:
! The ground water beneath the site has been contaminated by hazardous substances emanating from the landfill. Both
the shallow and deep aquifers have been affected.
! Potable residential wells have been contaminated with various chemicals that have migrated offsite.
! Other wells farther downgradient of the site are at risk because of the continued offsite migration of the contaminated
ground water.
The technical components of the recommended alternative were proposed in a single ROD and are as follows;
! Provision of an alternate water supply and, while the alternate water supply system is under construction, provision of
bottled water for affected residents
! An active collection and treatment system for landfill gases
! Expanded environmental monitoring of water, air, soils, and leachate
! A cap that covers the landfill
! Pumping and onsite treatment of shallow ground water and leachate
! Surface water controls to accommodate runoff
! A second-phase feasibility study to evaluate the need for remediation of the deep aquifer
The main concern over pumping deep wells is the possibility of drawing contaminated water down from the shallow aquifer.
Because of the fractured nature of the bedrock, patterns of vertical flow and recovery are difficult to predict. Consequently, a more
reasonable approach was to remediate the shallow aquifer to achieve the desired reduction in contaminant levels and then evaluate
the need for deep aquifer pumping in a second-phase feasibility study. If vertical connections exist, pumping would be initiated in
the deeper zone, if necessary, when contaminant levels in the shallow zone no longer pose a threat.
3.2.2.1 Interim Actions to Prevent Exposure
If the removal action levels discussed in Section 3.2.1.1 are
exceeded and the site otherwise qualifies for removal
response (that is, the action can be accomplished within the
$2-million/12-month limits or satisfies the criteria for
exemption), a removal action would generally be considered.
If exposure to contaminants does not meet the criteria for a
removal action, but drinking water supplies are threatened or
have been affected at levels below the removal action levels,
however, an interim action can be considered. Interim actions
for ground water are appropriate when there is enough
information (e.g., contaminants of concern are identified) to
determine which remedial technology or process option (e.g.,
well head treatment or an alternate water supply) will be
selected. It may not be necessary to complete a detailed FS
since there will probably be a limited number of alternatives to
consider. Exhibit 3-3 presents an example of an interim action
that was implemented to prevent exposure to contaminated
ground water.
3.2.2.2 Interim Actions to Prevent Further Degradation
of Ground Water
If contaminants are migrating away from the source or from a
contaminant hot spot and action can be taken to prevent
expansion of the ground-water plume, an
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Exhibit 3-3. Interim Action: Alternate Source of Drinking water
In Charlevoix, Michigan, an interim action was taken to supply the town with an alternate permanent source of drinking water. An
RI/FS was subsequently completed to investigate the location of the source and the extent of contamination. A focused FS was
conducted to evaluate alternatives for supplying water to Charlevoix, a town an Lake Michigan with a population of 5,000 during
the summer months. The town well was contaminated with 50 parts per billion (ppb) of trichloroethene, and monitoring wells
upgradient of the town well indicated that higher concentrations of both ttichloroethene and tetrachloroethenes were moving toward
the well.
Several alternatives were considered:
! Installation of new city wells
! Provision of bottled water
! Use of an adjacent community's water
! Installation of home treatment systems
! Treatment with granular-activated carbon or air-stripping
! Treatment of Lake Michigan water
The alternative selected was to design an intake and treatment plant for the use of Lake Michigan water. In conjunction, well use
restrictions in the area were implemented; wells may only be installed if a permit is obtained. Installation of new wells was rejected,
because a new wollfield would have to have been located a substantial distance away from the town, as contamination was
extensive in the large sand aquifer underlying the town. Water supply was inadequate in adjacent communities. Treatment
alternatives were substantially more expensive than most of the other options, and bottled water and home treatment systems did
not provide reliable long-term protection. Bottled water was supplied, however, until the selected alternative was in place.
The interim action evaluation was completed in 6 months, and a ROD was signed in 1984. Design and construction of the treatment
facility took place approximately 1 year later. The full RI/FS was completed at about the time plant startup began, at which time a
second ROD was signed.
Two factors motivated the rapid selection and implementation of this alternative: the town's sole source of drinking water was
contaminated; and an alternate source of drinking water with unlimited supply and limited treatment requirements was available.
interim action to prevent further degradation of ground water
while the RI/FS is being completed can be taken. The benefits
of an interim action must be balanced with the possibility that
the plume will be drawn farther away from the source because
of the early stage of the investigation and consequent lack of
information about the site. Key factors to consider in
determining whether to implement this type of interim action
include:
! The estimated rate of plume expansion-this may be
the primary factor for determining the
cost-effectiveness of taking the action before the full
RI/FS has been completed. If the contaminants
potentially will migrate vertically or horizontally during
the RI/FS, the cost of restoring this additional area of
the plume should be considered in light of the
cost-effectiveness of initiating the early action.
! The location of sources contributing to the
ground-water contamination-if the sources of
ground-water contamination have not been fully
defined, the interim action could increase migration
of contaminants from unidentified sources.
Contingency measures should be outlined in the
description of the remedy, and
methods to evaluate whether or not they are
necessary should be implemented. This may include
placement of monitoring wells upgradient of the
contaminated area so that unidentified plumes are
detected before they reach the extraction wells.
! The stage of plume characterization-initiation of
ground-water extraction could alter the plume such
that concentration gradients are no longer
continuous. If the horizontal and vertical extent of
contamination at the site has not been completely
defined, the resulting distortion may make full
definition of the plume difficult.
Exhibit 3-4 presents an example of an interim action that was
implemented to prevent further ground-water degradation.
3.3 Project Planning--Data
Collection Activities
Data collection activities should be efficiently organized and
focused on site-specific issues. Before identifying specific
data collection activities, the following should be
accomplished:
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Exhibit 3-4. Interim Action: Preventing Further Ground-Water Degradation
An Interim action was taken at Tacoma well 12A before completion of the RI/FS to prevent the contaminant plume from contaminating
the entire well field.
Tacoma well 12Awasoneof 13 production wells serving the City of Tacoma, Washington, during peak summer water demand. Well
12A had been found to be contaminated with approximately 500 parts per billion of 1,1,2,2-tetrachloroethane as well as by smaller
concentrations of a few other volatile organic compounds. Monitoring wells installed in 1981 and sampled from 1981 through 1983
had indicated the general extent of the plume. Well 12A was believed to be located at the leading edge of the plume, which was
upgradient of the well field during the summer pumping season when the natural ground-water flow is reversed. There was concern
that operation of the well field to meet peak water demand would draw contamination into the rest of the well field.
The interim action involved designing an air-stripping system for well 12A, which was then pumped continuously to act as an
interceptor well. Low levels of contamination in an adjacent well disappeared following initiation of pumping at the interceptor well.
The air-stripping design allowed treated water to enter the drinking water system. The system was still in operation in 1988.
The benefits of the interim action include:
! The interim action was implemented rapidly, in time for use during the peak demand period
! The well field was protected from contamination
! Only one air-stripping system had to be installed
The project took about 6 months to complete from the time a ROD was signed. The RI/FS for the project was completed in
approximately 2 years, when another ROD was signed.
A ground-water treatment system at the source was subsequently installed.
The factors that made this interim action possible included:
! A general understanding of the relationship of the source to the well field
! Contaminants amenable to treatment
! Information on contaminant concentration such that the inlet design criteria of the air-stripping system could be specified
! Active cooperation by local, State, and Federal agencies
Without knowing plume concentration and extent, design of the system would have been less certain.
! Any existing or imminent exposures should be
eliminated using removal authority as discussed in
i
Section 3.2.1
Potential exposure pathways should be identified
! Site-specific questions related to aquifer class and
appropriate response should be considered
! A thorough examination of existing data should be
completed before collecting additional data during the
Rl
The potential exposure pathways are generally identified
before RI/FS activities have been initiated. Figure 3-3
illustrates potential exposure pathways at sites with
contaminated ground water. If ground water at any depth
below the site could be used for drinking water, any
abandoned wells that could serve as conduits for contaminant
movement to uncontaminated aquifers should be located.
Method for Determining the Locations of Abandoned Wells
(NWWA, 1987) provides guidance on this subject.
The evaluation of existing data includes evaluating logs of
existing wells in the area to provide geologic
information. Other sources of existing data that provide
information for scoping are listed in Table 2-1 of the RI/FS
Guidance. Information can also be obtained from the U.S.
Geological Survey or State and local agencies that collect and
inventory hydrogeologic and well-construction information.
A thorough site-specific data-collection strategy will be
organized to address the investigation goals listed below.
Questions to focus these data collection activities are
presented in Table 3-1.
! Characterization of the hydrogeology (i.e., geology
and ground-water hydrology, including aquifer
properties)
! Characterization of contamination (i.e., plume size
and composition)
i
i
Evaluation of plume movement and response
! Assessment of design parameters for potential
treatment technologies
Consideration of technical uncertainty
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Contaminant
Source
Contaminant
Release
Contaminant
Transport
Receptor
Point
Exposure
Route
Exposed
Population
Ingestion
Inhalation
Dermal Absorption
>,
Ingestion
Inhalation
Dermal Absorption
> Inhalation
> Dermal Absorption
> Inhalation
> Dermal Absorption
. Ingestion
, Inhalation
i Dermal' Absorption
> Incidental Ingestion
> Inhalation
> Dermal Absorption
> Uptake by Aquatic
Organisms
i Aquatic Organisms
> Site Users
* Terrestrial Organisms
That Ingest Aquatic
Organisms or Water
»People Who Fish &
Hunt at the Site or
Drink the Water
, Inhalation
i Dermal Absorption
Figure 3-3 Exposure Pathway Related to Ground Water.
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Table 3-1. Questions to Focus Data Collection Activities
Level of Contamination
-Will contaminants continue to migrate from the source to the ground water at levels that exceed
health-based or environment-based standards?
-Is current ground-water contamination above health-based or environment-based levels?
-Is there a significant potential for contamination above health-based or environment-based
levels?
-Will natural attenuation result in contaminant levels below health-based or environment-based
levels?
-Which ground-water classification describes the ground water?
Exposure to
Contamination
on the Basis of
Ground-Water
Classification
Class I or IIA -Is any domestic well water contaminated above health-based levels?
-Is an alternative water supply in use?
-Is the ground water ecologically vital?
Class IIB -Are unaffected downgradient wells that serve substantial populations irreplaceable?
-Is there a reasonable potential for domestic, agricultural, or other beneficial uses of water from the
area of the plume?
Class III
-Could the contamination migrate and contaminate Classes I, IIA, or IIB ground water or surface
water?
Single Non-
aqueous Phase
-Is the flashpoint of the non-aqueous phase below 80 degrees F?
-Is metal removal required?
-Can the non-aqueous liquid be recycled?
Contaminant
Properties
Affecting
Treatment
Single Aqueous
Phase
-Is metal removal required?
-If all the metals in the waste concentrate in the sludge, will the sludge be a hazardous waste?
-Will concentrations in the sludge be above the land disposal restrictions, or must sludge be treated
meet ARARs?
-Is organic removal required and feasible?
-Are the organics toxic to biomass?
Mixed Phases
-Will pumping result in an emulsion?
Response
Action
Natural
Attenuation
Containment
-Will natural attenuation result in contaminant levels below health-based or environment-based
levels at all wells?
-Would natural attenuation of the plume result in significant sp
health-based or environment-based levels beyond current bi
I read of contaminants above
oundaries?
-Would the plume enter surface water where the resultant concentration of a contaminant would
increase to a statistically significant level?
-Is there confidence that institutional controls within the boundaries of the plume would be
effective during natural attenuation, considering growth rate in the area and other potential
increases in water demand?
-Would a containment system be effective in limiting plume expansion during extraction?
-Are contaminants amenable to containment by a slurry wall?
-Would a slurry wall be technically feasible to construct?
-Would construction of a slurry wall result in adverse environmental impacts?
-Would a low-rate pumping system or French-drain system be technically feasible to construct
and operate?
(continued)
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Table 3-1. Continued
Response Extraction &
Action Discharge
(continued)
Biodegradation
-Is the aquifer amenable to extraction, considering transmissivity, interconnection, etc?
-Can any surface water in the vicinity accept treated discharge?
-Would a ground-water recharge option such as infiltration trenches or spray irrigation be
feasible?
-Is a publicly-owned treatment works (POTW) available for discharge?
-Can permission be obtained to discharge to the POTW?
-Will pretreatment be required before discharging to the POTW?
-Is the site environment compatible with biodegradation considering climate, soil, biota, surface
water, and ground water?
-Can the waste be treated biologically considering physical and chemical characteristics, toxicity,
enhancement requirements, degradabitity of related compounds, and by-products of
degradation?
-Is on-site or off-site biodegradation prevented by regulation?
-Will biodegradation increase the mobility of contaminants and possibly worsen the ground-water
contamination threat?
-Will safety or environmental considerations preclude biodegradation as an alternative
considering site and waste characteristics?
-Will public health and welfare considerations prevent the timely use of biodegradation?
Each of these goals is described in the sections that follow.
To ensure that the data generated to address these goals are
adequate to support a decision, a clear definition of the
objectives and the method by which decisions will be made
must be established early in the project planning phase.
These determinations are facilitated through the development
of qualitative and quantitative data quality objectives (DQOs)
specified to ensure that data of known and appropriate quality
are obtained in support of remedial actions and Agency
decisions. The process for determining DQOs is described in
detail in Data Quality Objectives for Remedial Activities (DQO
Manual) (U.S. EPA, 1987d)
Sources of technical information that describe the design of
remedial alternatives are referenced throughout the following
discussion. In addition, regional and EPA laboratory
representatives have formed a ground-water forum that meets
periodically to discuss technical issues that have arisen at
sites; members of this forum may be contacted to discuss
technical concerns. Also, the ground-water work station, an
analytical ground-water computer system, is available at the
Regions to assist in visualizing and modeling ground-water
contamination (U.S. DOE, 1986 and 1988).
3.3.1 Characterization of the Hydrogeology
To analyze data relating to the distribution and movement of
contaminants in the subsurface, it is necessary to understand
the site hydrogeology. Pertinent information includes the
physical properties and three-dimensional characteristics of
the geologic formations; the ground-water hydrology including
location of recharge and discharge zones, piezometric surface
for each hydrogeologic unit, seasonal or long-term fluctuations
in water levels for each unit; and the hydraulic properties
(transmissivity, storage coefficient) of the aquifers and
aquitards.
3.3.1.1 Geology
The majority of information regarding the geologic formations
and related structures underlying the site will be obtained
through the description of sediment samples collected
during drilling of soil borings and monitoring wells. It is
worthwhile to describe all strata underlying the site to at least
the maximum depth of known or potential contamination
and generate a reliable and complete description
of the subsurface geology. Continuous
core samples can be collected using auger or rotary drilling
methods. In addition to laboratory analysis, in
situ analysis can also be made of the geology through
borehole and other geophysical methods. These methods can
provide many of the same parameters determined through
laboratory analysis, at a reduced cost. Other geophysical
methods can provide information on the extent of certain
plumes, areas of buried trenching operations, and abandoned
well locations.
The information obtained during the geologic investigation can
be presented in geologic cross sections and fence diagrams.
Laboratory analysis of sediment or rock samples may include
grain size analysis, plasticity, moisture content, dry density,
clay
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mineralogy identification, partition coefficient for pertinent
chemicals, and hydraulic conductivity.
3.3.1.2. Ground-Water Hydrology
Ground-water movement can be analyzed through the
measurement of water levels in wells and piezometers. It is
helpful to categorize wells according to the elevation and
geologic formation of the screened interval so that the
horizontal and vertical gradients of hydraulic potential can be
analyzed separately. If there are enough measuring points, a
contour map of the piezometric surface of each aquifer can be
prepared. The contour map can be evaluated to determine
possible areas of ground-water recharge and discharge and to
identify the direction of ground-water movement. Water level
data collected from all the wells on the same day provides the
most representative information for producing a potentiometric
surface map. In addition, to indicate the magnitude and period
of fluctuations as well as any long-term change in water
levels, it is generally recommended that data be collected
from a subset of wells over a period of time and plotted as a
hydrograph to determine short-term tidal fluctuations or long-
term seasonal fluctuations.
3.3.1.3 Aquifer Properties
Aquifer tests can be used to determine the hydraulic
properties of the aquifers and aquitards within the area of
interest, and to evaluate the performance and effectiveness of
an extraction system. These test are conducted by artificially
causing ground-water movement either through pumping or
injecting water and then monitoring the fluctuations in ground-
water levels.
Aquifer test are conducted to measure aquifer parameters
such as transmissivity, hydraulic conductivity, and the storage
coefficient. These parameters are used to estimate the
ground-water flow rate, the optimal pumping rate for ground-
water extraction, proper well location, and plume migration
behavior. Vertical hydraulic conductivities can be evaluated by
monitoring the water levels in observation wells that are
screened at different depths than the pumping well.
It is beneficial to conduct aquifer pumping tests during an
RI/FS whenever ground-water extraction is expected to be part
of the remedy. Because one of the objectives of an aquifer
test during RI/FS activities may be to design an extraction
well system, the most accurate information will be obtained
when the pumping well is placed in the same formation and
pumped at the same rate as the proposed extraction system.
When scoping an aquifer test, it is important to consider
disposal of contaminated ground water (see Section 2.4.1 for
potential requirements for this discharge). Temporary onsite
storage of treated water may be required if the water cannot
be discharged.
Additional information on aquifer tests can be found in Applied
Hydrogeology (Fetter, 1988) and Groundwater and Wells
(Driscoll, 1986).
3.3.2 Characterization of Contamination
This section presents technical information about methods
used to characterize the hydrogeology and ground-water
contamination of a site. Topics discussed include indicator
chemicals, plume definition, and contaminant-soil interaction.
Although not discussed in this guidance, source areas also
should be defined to characterize contamination that might
pose as ongoing threat to the ground water.
Information about the contaminant mix and spatial distribution
of the plume is generally needed to select and analyze
remedial alternatives during screening and detailed analysis
phases. Physical and chemical properties of contaminants,
such as density and solubility, should be assessed because
they influence plume movement. It should be recognized that
some contaminants may not be detectable using routine
analytical services, though they are present at levels that
would be above cleanup levels. In these cases, special
analytical services, may have to be used.
3.3.1.1 Indicator Chemicals
Indicator chemicals are those site contaminants that are
generally the most mobile and toxic in relation to their
concentration; consequently, they reflect the majority of the
risk posed by the site. Generally indicator chemicals are
selected on the basis of toxicity, mobility, persistence,
treatability, and volume of contaminants at the site. By initially
identifying these constituents and then limiting analysis to
those constituents during the investigation, analyzed costs
can be reduced. During initial testing of the remedial action,
however, samples should be analyzed for all contaminants
present to ensure that indicator chemicals have been
appropriately selected.
Indicator chemicals are used during modeling and during
some monitoring activities to reduce cost and simplify
characterization of the site and remedial alternatives. Samples
are generally analyzed once for total metals, cyanide, semi-
volatiles, volatiles, and major anions and cations; periodically
for those contaminants found at the site; and more frequently
(e.g., during aquifer tests) for indicator chemicals. Before
completing the remedial action, samples should be analyzed
for all contaminants originally detected.
All migration pathways should be considered when
determining indicator chemicals, particularly when the
proposed treatment results in transferring contaminants
between media. For example, chemicals
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treated in an air stripper may cause inhalation threats but not
ingestion threats. Consequently, those chemicals should be
considered for selection as indicator chemicals. Chemical
structure may also guide selection of indicator chemicals
since chemicals with similar structure often have similar
properties; this is the basis of quantitative structure-activity
relationships (QSAR), which are discussed in the scientific
literature. One method for selecting indicator chemicals can
be found in the Superfund Public Health Evaluation Manual
(U.S. EPA, 1986f).
3.3.2.2 Plume Definition
Determining both the horizontal and vertical extent of a
contaminant plume is a complex problem. In addition to
sampling ground-water monitoring wells, a wide variety of field
techniques such as soil gas analysis and geophysical
surveys (U.S. EPA, 1988g) can be used to obtain relevant
data. The locations of the monitoring wells should be
determined from ground-water flow directions estimated from
existing site data. It is best to obtain the advice of someone
with hydrogeology experience to determine where to place
wells and at what depth they should be screened on a site-
specific basis. It is usually most efficient to install wells in a
phased approach, i.e., increasing the distances from the
source area in three dimensions with each subsequent round
of investigation. Sources and methods for obtaining the
information needed to assess the extent and movement of a
ground-water plume are listed in Table 3-7 of the RI/FS
Guidance. Technical details of methods listed in the table can
be found in the Compendium of Superfund Field Operations
Methods (Compendium ) (U.S. EPA, 1987c) and the RCRA
Ground-Water Monitoring Technical Enforcement Guidance
Document (TEGD) (U.S. EPA, 1986e). When it becomes
clear that contaminants have migrated beyond property
boundaries, and effort should be initiated to identify
neighboring property owners and obtain access to the
properties necessary to complete the investigation. The
Superfund Enforcement Branch at EPA Region IX has
prepared a sample letter requesting property access. A copy
of this letter is provided in Appendix F.
3.3.2.3 Contaminant-Soil Interaction
Since ground-water extraction is frequently a component of
ground-water remediation, it is important during site
characterization to collect the data needed to estimate the
effectiveness of pumping to remove contaminants to cleanup
levels. The sorption characteristics of the particular soil and
contaminants present at the site affect extraction and can
substantially increase the restoration time frame for remedies
that depend on extraction of ground water. Core sampling and
the resultant analysis of the saturated zone can provide
important sorption data.
While extensive sorption data may not be needed to extract
dissolved product or pure organic phase liquids that are lighter
than the aqueous phase, it is difficult to extract residual
ground-water contamination that has saturated the soil such
that levels remaining are predicted to continue to cause
ground-water contamination above health-based levels.
The partition coefficient (Kp) can be used to indicate the
tendency of a contaminant to sorb to the soil from the ground
water and desorb from the soil to the ground water. The Kp is
defined as the ratio of the concentration of contaminant in soil,
g/g, to the concentration of contaminant in ground water,
g/ml. For organic compounds, the Kp can be estimated using
the fraction of a contaminant that is in the aqueous phase and
from an analysis of total organic carbon. Thermodynamic and
kinetic variables can be used to estimate Kp for metals.
More accurate values for Kp are obtained from direct
measurements in bench scale sorption studies. Studies
should be designed to measure desorption as opposed to
adsorption or absorption because the mechanism for
desorption is frequently different. While estimated values of Kp
are of adequate precision in some cases, it may be desirable
to reduce uncertainty. Estimated values of Kp often are only
precise to three to five orders of magnitude while values
determined in the laboratory are generally accurate to within
one to two orders of magnitude.
3.3.3 Analysis of Plume Movement and Response
Ground-water modeling performed during the RI/FS process
can be used as a tool to estimate plume movement and
response to various remedies. However, caution should be
used when applying models at Superfund sites because there
is uncertainty whenever subsurface movement is modeled,
particularly when the results of the model are based on
estimated parameters.
The purposes of modeling ground-water flow include the
following:
! Guide the placement of monitoring wells and
hydrogeologic characterization when the Rl is
conducted in phases
! Predict concentrations of contaminants at exposure
points
! Estimate the effect of source-control actions on
ground-water remediation
! Evaluate expected remedy performance during the FS
so that the rate of restoration can be predicted and
the cost effectiveness comparisons can be made
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Various models are available to predict contaminant
concentrations and remedy performance. These vary in the
number of simplifying assumptions that must be made, the
cost of running the model, and the level of effort needed.
More complex models incorporate more information and
require more data and expertise to run. Regardless of the
complexity of the model, however, representative input data must be
used to obtain reliable results, and the results of the models must be
interpreted correctly. The determination of whether or not to
use modeling and the level of effort that should be expended is
made on the basis of the objectives of the modeling, the ease
with which the subsurface can be conceptualized
mathematically, and the availability of data. Figure 3-4
presents a flow chart of the decisions and the activities
associated with formulating and implementing a ground-water
model. A case study illustrating how models might be used at
a Superfund site is presented in Exhibit 3-5.
Table 3-2 lists some of the processes evaluated and variables
used when modeling ground water. Field data are collected to
characterize some of the variables listed in the table.
Estimates based on literature values or professional judgment
are frequently used as well. The factors listed in the second
column of Table 3-2 are not typically modeled but can
significantly affect contaminant movement at some sites.
These factors should be considered qualitatively when
appropriate. Information on ground-water modeling can be
obtained from the Center of Exposure Assessment Modeling,
Athens, Georgia, (phone number 404/546-3546) and the
International Ground-Water Modeling Center at Butler
University, Indianapolis, Indiana. In addition, the Office of Solid
Waste (OSW) is preparing guidance on the implications for
modeling the factors in Table 3-2 in the forthcoming Handbook
of Assessment and Remediation of Contaminated Ground
Water. Finally, the Office of Health and Environmental
Assessment has developed guidance on modeling for
exposure assessments (U.S. EPA, Review Draft, June 1987).
3.3.4 Assessment of Design Parameters for
Potential Treatment Technologies
A range of remedial alternatives is identified early in the RI/FS
process to focus data collection activities on remedy
selection. The design of many remedial technologies requires
data that may not generally be collected during the Rl. It is
important to consider data needs for design during scoping to
reduce the amount of time needed to select and implement
the remedy. Table 3-3 list some of the data needs for
evaluation and design of various remedial technologies.
Frequently, the best way to develop meaningful and reliable
design criteria is to conduct a treatability
study to establish the effectiveness of a particular remedial
alternative or remedial technology. The need for treatability
studies should be identified during the scoping process when
possible so they can be initiated early in the RI/FS to avoid
affecting the overall project schedule. The advantages of
treatability studies should be weighed against the increase in
time and cost for conducting them.
Other site-specific information can affect remedial design. An
example of site-specific information that may be important to
evaluate is the presence of naturally occurring radionuclides
at a site. Radionuclides extracted with the contaminated soil
vapor or ground water may accumulate on the collection
media designed to remove the site contaminants. If buildup of
radionuclides on the collection media is found to occur there
is the potential for personnel exposure problems and
additional transportation and disposal requirements. A study
assessing the potential for this type of buildup to occur is
under way in a joint project being conducted by OERR and
the Office of Radiation Programs.
3.3.5 Technical Uncertainty
This section describes situations in which technical
uncertainty can arise and discusses how to address technical
uncertainty so that cost-effective decisions can be made
about data collection.
Data collected during the Rl are used primarily to support a
cleanup decision. It is important to recognize that some
technical uncertainty is inherent in RI/FS process. Reducing
this uncertainty should be weighed against time and resource
limitations, and often remedy selection should move ahead
using best professional judgment even if the level of
uncertainty is high. The value of collecting and analyzing
additional data for remedy selection is related to how much
the information helps distinguish remedial alternatives and
what the technical uncertainty is of the performance of these
alternatives.
Technical uncertainty arises from the following determinations:
! Predicting the nature, extent, and movement of
contamination
- Source volume, concentration, and timing of
release
- Physical, chemical, and biological
characteristics of contaminants
- Contaminant dispersion and diffusion
! Determining contaminant movement through the
vadose zone
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Exhibit 3-5. Ground-Water Modeling at a Superfund Site
An abandoned industrial facility was found to be contaminating ground water when solvents were detected at low levels at a nearby municipal well.
The site was listed on the National Priorities List, and an RI/FS was initiated.
Background
Soil at the site was found to be contaminated with several volatile organic compounds including tetrachloroethene, trichloroethene, vinyl chloride, and
trans-1,2- dichloroethene. To characterize the extent of the soil contamination, a soil sampling grid was set up at 50-foot centers in the suspected source
areas, and samples were taken at 2.5-foot intervals in the saturated zone, which terminated in bedrock. Samples were also collected from the bedrock
layer to determine contaminant migration at this depth. From analysis of the soil and bedrock samples, the total mass of contaminants was estimated.
A source control remedy to remove the most highly contaminated soils in the unsaturated zone was completed to prevent further degradation of the
ground water. Also, ground-water wells were installed at several of the boring locations. Samples of ground water indicated that concentrations of
volatile organic solvents had reached levels as high as 50 ppm. Because the municipal well was screened in the contaminated aquifer, pumping at this
well was temporarily stopped to prevent further spreading of the plume.
On the basis of data taken from the municipal well, the aquifer was determined to be permeable enough to use extraction practicably. It was anticipated
that a large mass of contaminants would be extracted with the ground water because the solubilities of many of the contaminants were high. Therefore,
ground-water extraction and treatment was expected to be part of the ground-water remedy at this site. An aquifer test was performed to determine
the optimal pumping rate.
To actively restore the ground water to health-based levels and remove remaining contaminants from the unsaturated zone, it was proposed to dig
trenches and flush the aquifer by reinjecting treated ground water to the saturated zone. The low levels of contaminants found in the bedrock layer were
predicted to be removed because pumping the upper zone would induce an upward vertical gradient in the bedrock formation.
The remedial action objectives were as follows:
! Cleanup levels for individual constituents were based on health-based levels for drinking water and result in a total volatile organics (TVO)
concentration of 80 ppb
! The area of attainment includes the entire contaminant plume because, upon completion of the proposed remedial action, there will be noonsite
containment or management of waste
! The restoration time frame was estimated using several modeling approaches as described in the next section
Modeling Restoration Time Frame
Three ground-water models were used to reflect the site situation and evaluate the sensitivity of the predicted restoration time frame to various parameter
estimates and physical processes:
! Batch flushing model
! Continuous flushing model
! Simple advection/dispersion model
Batch Flushing Model. The batch flushing model was used to calculate the restoration time frame an the basis of equilibrium batch flushing. This model
takes into account the porosity of the soil, the organic carbon partition coefficient of the contaminants, the organic content of the soils, and the
ground-water pumping rate. The soil porosity and organic content were determined from field data while the organic carbon partition coefficient was
estimated from the literature (Lyman, 1982). The soil/water partition coefficient was calculated from the product of the fraction of organic carbon in soils
and the chemical-specific organic carbon partition coefficient:
Kd = KOC x foe
where
K(j = soil/water partition coefficient
KQC = organic carbon partition coefficient
foe = fraction of the soil that is organic carbon
The number of pore volumes (aquifer flushes) per unit time could be calculated using estimates of the optimal ground-water pumping rate, the volume
of contaminated area, the porosity of the soil, and the partition coefficients for the various contaminants. Using the batch flushing model, remedial action
to 80 ppb of TVOs was estimated to take approximately 27 years. A more detailed description of this calculation can be found in Appendix D.
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Exhibit 3-5. Continued
Continuous Flushing Model. The continuous flushing model uses a laboratory-derived leaching rate (partitioning) constant to determine the time it would
take to flush the volatile organic compounds out of the saturated soils. A mass balance approach is used to calculate contaminant concentration changes
with the number of control volumes of contaminated soils (the control volume is a unit volume of soil). This information is then used to determine the time
required to reach cleanup levels throughout the entire plume. The application of this model requires contaminant concentration data for both the saturated
soils and the ground water, in addition to the leaching rate constant The fundamental mass balance relationship is as follows:
VOC mass in VOC mass in VOC mass VOC mass leached
ground water = ground water - removed through + into ground
at time t at time t-1 pumping water from soil
The leaching rate constant was determined from bench-scale tests of three saturated soil cores of varying contaminant concentrations. This model
predicted a restoration time frame of 9 years. A more detailed description of the model is found in Appendix D.
Advection/Dispersion Model. The simple advection/dispersion model assumes steady-state flow with an instantaneous release of contaminants into
ground water. This model requires estimating the coefficient of molecular diffusion for the contaminants and takes into account the fact that diffusion
is occurring in a porous medium. As the contaminant mass is transported through the flow system, the concentration distribution of the contaminant mass
at time t is given by the following expression:
M -X2 Y* Z2
**** 5Urrrt3/2 D D DVZ 4D t 4D t 4D t
x y z x ^ z
where:
C = concentration
M = mass of contaminant introduced at the point source
t = time
Dx,y,z = coefficients of dispersion in the x, y, and z directions
X, Y, Z = distances in the x, y, and z directions
This model calculated a restoration time frame of 5 years. A more detailed description of this model can be found in Groundwater (Freeze and Cherry,
1979, page 395).
Summary
By using three different models, the effect of the model assumptions on the projected restoration time frame could be evaluated. The restoraton time
frames predicted by the three models are summarized below:
Model Treatment Time
Batch flushing 27 years
Continuous flushing 9 years
Advection/dispersion 5 years
The batch flushing model predicted a longer restoration time frame than either of the other models because it used the concentration of VOC contaminants
in ground water to calculate the theoretical concentrations in soil. Because the calculated soil contaminant concentrations were higher than the soil
concentrations determined from sampling and analysis, it was determined that this model did not adequately predict actual site conditions. The higher soil
concentrations caused the model to predict a longer restoration time frame, which appeared to be unrealistic.
The continuous flushing model is based on site soil and ground-water data as well as an experimentally-derived leaching constant. For these reasons,
it was the preferred model. The model is very sensitive to the dynamic leaching constant; therefore, it was important to collect representative soil cores
from the site. Extensive soil and ground-water data were also needed to accurately assess the extent of contamination.
The advection/dispersion model greatly oversimplified the site hydrogeology and chemical characteristics of adsorption and partitioning and for this reason
underestimated the treatment time needed to restore the aquifer to the desired cleanup levels.
References:
Lyman, W. J., W.F. Reehl, and D.H. Rosenblatt, Handbook of Chemical Property Estimation Methods, McGraw-Hill, New York, 1982. Freeze, R.A.
and J.A. Cherry, Groundwater, Prentice Hall, Inc., Englewood Cliffs, New Jersey, 1979.
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Change Assumptions,
Choose New Model,
Change Parameter Values
No
Formulate Problem
Cleanup Levels
Exposure Scenarios
Restoration Time Frame
Conceptualize
Physical System
Will an
Available Model
Simulate the Physical
System
Does
"Model Match Historical
Data
Yes
Collect Additional Data
or Use Best
Professional Judgment
>
Yes
Estimate Parameter
Values to Be Used
as Model Input
5
r
Solve Equations;
Perform Model Executions
>
f
Calibrate Model
>
I
Impose
New Conditions and Forecast
System Response
Figure 3-4 The Steps of Formulating and Implementing Ground-Water Model.
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Table 3-2. Processes and Variables Applicable to Ground-Water Modeling
Processes and Variables Frequently
Incorporated in Models'11
Processes and Variables That
Should Be Considered
Qualitatively (2)
Physical
Chemical
Biological
Flow in saturated porous media
- advection
- hydrodynamic dispersion
- molecular diffusion
- density stratification
- aquifer properties and heterogeneities
- hydraulic head distribution
- hydrogeologic boundaries
- aquifer recharge
- evapotranspiration
Radionuclide decay
Sorption
Flow in fractured media
Particle transport in any medium
Flow in unsaturated porous media
Multiphase flow in any medium
Redox reactions
Ion exchange
Complexation
Co-solvation
Volatilization
Precipitation
Microbial population dynamics
Substrate utilization
Biotransformation
Adaptation
Co-metabolism
(1)Site-specific conditions will determine which data are required to model desired processes or determine
variables.
(2)These processes and variables can be modeled, but such models are state-of-the-art.
- Hydraulic conductivity and soil water potential
- Moisture content of soil
- Chemical and biological characteristics of soil
Estimating the rate and direction of the ground-water flow
- Hydraulic conductivity (viscosity, density, permeability)
- Anisotropy and heterogeneity of hydrogeology
- Aquifer characteristics (porosity and organic carbon
content)
- Aquifer stresses arising, for example, from ground-water
pumping at other wells and infiltration (naturally and
artificial recharge)
- Seasonal variation in ground-water levels
- Tidal/pressure effects
- Storage characteristics of the aquifer
- Aquifer thickness and areal extent
Estimating the cost of remedial alternatives
When deciding how much information to collect, one should
examine the extent to which the additional information will
reduce the uncertainty of remedy selection and predicted
performance of remedial alternatives (e.g., see the discussion
on contaminant-soil interactions in Section 3.3.2.3). For
example, in deciding how much uncertainty is acceptable for
hydraulic conductivity, one should consider how much the
uncertainty in hydraulic conductivity affects uncertainty in
remedy selection. If the additional information allows one to
distinguish between two alternatives, it is probably worthwhile
to collect the information. Frequently, however, it is not
possible to significantly reduce the uncertainty in the variables
that contribute most to the overall uncertainty of the decision.
To assess the effect of uncertainty in some variables a
sensitivity analysis can be performed. A sensitivity analysis
evaluates how the uncertainty in particular variables affects
the predicted cost and effectiveness of the remedial
alternatives. To conduct a sensitivity analysis, values of
variables are systematically changed, and estimates of cost
and effectiveness are recalculated to determine the
importance of each assumption. Alternatively, a different but
equally plausible ground-water flow model could be used.
Uncertainty in variables that have the greatest effect on the
prediction of the uncertainty of remedy performance should be
closely examined.
Instead of conducting a formal sensitivity analysis, an
informal approach can be used to decide whether to collect
additional data to characterize a variable such as cost. In this
case, the two or three largest sources of uncertainty related
to characterizing cost should be identified. If the additional
data would reduce the uncertainty inexpensively and in a
reasonable period
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Table 3-3. Typical Technology Selection and Design Parameters
Technology Typical Screening Parameters
Typical Design Parameters3
Extraction
Air-stripping
Aquifer storage coefficient
Soil type/porosity
Hydraulic conductivity
Aquifer saturated thickness
Contaminant sorpton
Contaminant solubility
Contaminant volatility
Disposal of treated water
Aquifer parameters
Depth to the aquifer
Number of wells
Well extraction rate
Contaminant distribution
Presence of non-aqueous phase
Ground-water temperature
Influent flow rate
Contaminant concentrations
Carbon adsorption
Chemical destruction
(e.g., KPEG, peroxide
treatment)
Metals precipitation
Nonaqueous phase
separation
In situ biodegradation
In situ solvent wash and
extraction
In situ vapor extraction
In situ vitrification
Contaminant adsorptability
Total organic carbon
Disposal of treated water
Metals separation
Susceptibility to reaction
Total organic carbon
Metals solubility
PH
Metals concentration
Management of residuals
Disposal of treated water
Contaminant solubility
Contamination concentrations
Specific gravity
Soil type/porosity, permeability-primary and
secondary
Contaminant biodegradability
Aquifer properties
Distribution of microorganisms
Dissolved oxygen
Contaminant concentration
Soil type/porosity, permeability-primary and
secondary
Contaminant solubility
Sorption properties
Organic moisture content
Soil type/porosity, permeability- -primary and
secondary
Contaminant volatility
Contaminant concentration
Contaminant concentration
Depth of contamination
Area of contamination
Soil type/moisture content
Presence of reactive compounds
Electrical conductivity
Influent flow rate
Carbon adsorptive capacity
Contaminant concentrations
Influent flow rate
Dose of reactant
Contaminant concentrations
Influent flow rate
Alkalinity/acidity
Coagulant dosage
Contaminant concentrations
Influent flow rate
Total suspended solids
Nutrient requirements
Contaminant distribution
Injection/extraction well flow rates
Aquifer parameters
Biodegradation rate
Aquifer parameters
Depth to the aquifer
Contaminant distribution
Contaminant concentrations
Contaminant distribution
Well radius of influence
Extraction well flow rates
Hydraulic conductivity
Contaminant distribution
Underlying geology
Rate of carbon usage for off-gas treatment
aWhen possible, data for design can be collected during implementation of an interim remedy. Design parameters also include considerations such as
standards to be attained for all emissions to air and water and any generation of solid waste.
of time, then they should be collected. Exhibit 3-6 presents an
example of a sensitivity analysis.
If there is sufficient confidence that a particular remedy will be
effective for a site, a detailed evaluation, which is discussed
in Chapter 6, should be made. Data to reduce the uncertainty
of important variables should be collected throughout the
remedial selection, design, and construction phases to refine
and modify the remedy.
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Exhibit 3-6. Using A Sensitivity Analysis
To address the adequacy of the hydrogeologic data collected at the San Gabriel basin, and to improve the performance of a
ground-water model by further refining the estimates of model parameters, a sensitivity analysis was performed. The sensitivity
analysis evaluated the following model parameters:
! Hydraulic conductivity
! Specific yield
! Recharge from precipitation
! Artificial recharge
! Boundary conditions
! Ground-water pumping
The analysis consisted of the following:
! Varying a particular model parameter
! Rerunning the model for the first 5 years of the simulation period
! Observing the effect of the parameter vadation on both the simulated water levels and the calculated
ground-water velocity
From this analysis, it was found that the calculated velocity was highly variable within the basin. Velocity provided a useful
measure of the relative importance of the different parameters in predicting ground-water flow. The greatest degree of
uncertainty was associated with the vertical distribution of hydraulic conductivity. On the basis of the analysis, the
ground-water velocities calculated from the model were found to vary between 50 and 200 ft/yr. The original analysis of the
hydraulic properties of the basin led to estimates of hydraulic conductivity that were estimated to vary from 10 to 1,000 ft/yr.
Because the horizontal and vertical distribution of hydraulic conductivity, the areal distribution and magnitude of specific yield,
and recharge at spreading basins and from precipitation lead to the most uncertainty, additional data acquisition and analysis
would be most useful for these variables.
Because the San Gabriel site is very large (165 square miles) decisions about scoping may be very costly. Thus, an extensive
modeling effort was undertaken to provide initial information to develop data quality objectives. In summary, the sensitivity
analysis defined which parameters were critical, and the variance in ground-water velocity was reduced from 10 to 1,000 ft/yr
to 50 to 200 ft/yr. This approach led to a better understanding of the accuracy and precision of the results. On the basis of the
sensitivity analysis, areas of further data collection were identified and priorities were set.
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Chapter 4
Establishing Preliminary Cleanup Levels
4.1 Introduction
CERCLA requires that remedial actions be protective of
human health and the environment. In addition, remedial
actions must attain ARARs (unless a waiver is used). For
ground water that is a current or potential source of drinking
water, i.e., Class I or Class II, cleanup levels generally will be
based on chemical-specific ARARs or health-based levels.
This chapter presents information needed to establish
preliminary cleanup levels in the aquifer. The information
presented here is generally presented in the risk assessment
chapter of the Rl report. Preliminary cleanup levels should be
developed early in the RI/FS process and modified as more
information is collected. Final cleanup levels should be
presented in the FS and the ROD.
This chapter is organized into the following sections:
! Determination of cleanup levels
! Derivation of chemical-specific ARARs and
consideration of other pertinent materials
(to-be-considereds (TBCs))
! Assessment of aggregate effects
! Alternate concentration limits
! Summary
Ground water that is not a potential drinking water source
because of natural conditions (i.e., Class III ground water) is
not explicitly addressed in this chapter because health-based
cleanup levels for Class III ground water are usually not
appropriate. Environmental considerations (i.e., effects on
biological receptors) and prevention of plume expansion
determine cleanup levels for Class III ground water. Also, if the
Class III ground water is connected to ground water that is
Class I or Class II, it may be appropriate to set cleanup levels
at the point of interconnection, as described in the following
section. Further discussion of Class III ground water is
presented in Section 5.4.2.
Health-based cleanup levels for soil are usually based in part
on a soil ingestion exposure pathway. In addition, it is
generally appropriate to consider the potential for
contaminants to leach from soil to ground
water. By modeling the leaching rate of contaminants and
determining health-based levels in ground water, soil cleanup
levels can be calculated. Depending on the site soil,
consideration of leaching may tend to produce lower cleanup
levels than consideration of soil ingestion. A project to
compile a compendium of methods that have been used to
determine soil cleanup levels on the basis of the potential for
the contaminants to migrate to ground water is currently under
way at OERR. This compendium will be distributed to the
Regions as a resource.
4.2 Determination of Cleanup Levels
4.2.1 Process
Cleanup levels will generally be set at health-based levels,
reflecting current and potential use and exposure. For
systemic (noncarcinogenic) toxicants cleanup levels should
be set at levels to which humans could be exposed on a daily
basis without appreciable adverse effects during their lifetime.
For carcinogens, cleanup levels should reflect an individual
excess lifetime cancer risk that falls in the range commonly
expressed as the 10"4to 10"7unit risk range. The Agency
believes that remedial actions reducing risks to within this
range are generally protective of human health.
Often, ARARs, such as MCLs, will be used to determine
cleanup levels. However, ARARs may not be available or they
may not be adequate if multiple contaminants, multiple
pathways, or other factors present an aggregate risk that is
not sufficiently protective given the specific site
circumstances. In these circumstances, the appropriate level
of protection should be determined during the risk
assessment using Agency guidelines and other Federal
criteria, advisories, or guidances.
For ground water that is a current or potential source of
drinking water, MCLs set under the SDWA or more stringent
State standards devised to protect drinking water will
generally be ARARs. If MCLs are not available, proposed
MCLs should be considered. However, it is still necessary to
perform a risk assessment; aggregate risk should be
calculated for
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all contaminants in the ground water, including those with
MCLs. Aggregate risk is calculated using the risk-specific
dose (RSD) or the reference dose (RfD), as discussed in
Section 4.4.
If an ARAR does not exist for a contaminant, then TBCs
should be identified. RSDs, RfDs, health advisories (HAs), and
State or Federal criteria developed for waters other than
ground water are TBCs for ground water. MCLGs should be
consulted and may be relevant and appropriate if multiple
contaminants or multiple pathways warrant levels that are
more stringent than MCLs. Also, WQC should be considered
and may be relevant and appropriate at some sites,
particularly those sites where ground water discharges to
surface water that is used for fishing. WQCs may also be
relevant and appropriate when they are the most recent
health-based level that has been developed.
Generally, if cleanup levels for carcinogens are not determined
by ARARs, the 10"6 risk level should be the starting point for
the analysis of alternatives and the appropriate level of
protection. The use of 10'6 as an analytical starting point
expresses the Agency's preference for being at the protective
end of the risk range but is not a strict presumption that the
final remedial action should attain that risk level. The final
cleanup level and resulting risk level will be achieved by
balancing a number of factors relating to exposure,
uncertainty, and technical limitations.
Environmental effects must also be considered. WQC for
protection of aquatic organisms should be used when
Superfund sites pose potential environmental effects. Also,
some information on environmental effects may be available in
the scientific literature; see Verscheuren (1983), for example.
Additional information on environmental effects is available
from the User's Manual for Ecological Risk Assessment
(Barnhouse, 1986) and the eco-risk document currently being
developed by OSWER, entitled, "Superfund Environmental
Evaluation Manual."
The most common ARARs and TBCs are summarized in
Table 4-1, and Appendix E lists the values of these ARARs
and TBCs at the time of this writing. Figure 4-1 is a flow
diagram showing the decision path for identifying ARARs and
TBCs.
Figure 4-2 shows the process for developing ARARs and
TBCs from basic scientific information. This is discussed in
the following sections.
4.2.2 One Source of Common Health-Based
Criteria: The Integrated Risk Information
System
The Integrated Risk Information System (IRIS) is a computer-
based catalog of Agency risk assessment information for
chemical substances. Values for some of the TBCs are listed
in IRIS. This system is designed for Federal, State, and Local
environmental health agencies as a source of the latest
information about EPA's regulatory decisions for specific
chemicals. IRIS was developed by an intra-agency review
group in response to repeated requests for Agency risk
assessment information.
Chemicals found in IRIS are categorized on the basis of the
type of effect they cause. Chemicals that cause growth of
tumors are considered to be carcinogenic, while chemicals
that induce effects other than carcinogenicity or mutagenicity
are considered to be systemic toxicants.
EPA has developed a system for classifying the weight of
evidence of carcinogenicity in chemicals. The EPA carcinogen
classification system contains the following designations:
! Group A-Human Carcinogen
! Group B-Probable Human Carcinogen
! Group C-Possible Human Carcinogen
Evidence for the carcinogenicity of chemicals in humans
stems primarily from long-term animals tests and
epidemiological studies (studies of disease in human
populations). Short-term animal tests, pharmacokinetic
studies, structure-activity relationships, and other
toxicological information are also considered in developing a
framework for evaluating the weight of evidence of a
chemical's potential to be a human carcinogen.
Systemic toxicants are those believed to be toxic only at
concentrations above a threshold dose; doses below this
threshold are not expected to result in a significant adverse
effect. The mechanism for the toxicity of noncarcinogens
differs from that for carcinogens for which it is believed that
there is no threshold; any dose presents some incremental
risk (hence, the MCLG for carcinogens is set at zero). Some
chemicals can cause both systemic toxic and carcinogenic
effects.
The risk assessment information contained in IRIS, except as
specifically noted, has been reviewed and agreed upon by two
intra-agency review groups-the RfD work group and the
Carcinogen Risk Assessment Verification Endeavor (CRAVE)
work group. As these groups continue to review and verify risk
assessment-related information, additional chemicals and new
information will be added to IRIS. IRIS is available through
Dialcom's electronic mail, the computer-based electronic
communications system to which the EPA subscribes.
Further information on IRIS can be obtained by contacting the
Office of Information Resources Management, or IRIS
user-support, at (513) 569-7254, FTS-684-7254. Specific
details on the derivation of the chemical
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Table 4-1. Potential ARARs and TBCs
Primary potentially applicable or relevant and appropriate requirements (ARARs)
\ Promulgated State standards
! Maximum contaminant levels (MCLs)
Other potential ARARs and to-be-considereds (TBCs)
\ Proposed MCLs generally should be given first priority among TBCs.
! Risk-specific doses (RSDs)-To be considered when evaluating human health threats from carcinogens in drinking water
when MCLs, proposed MCLs, or State standards are not available, and for determining the risk level associated with an
ARAR.
! Reference doses (RfDs)-To be considered when evaluating human health threats from systemic toxicants in drinking
water. Use when MCLs, proposed MCLs, or State standards are not available, or when determining aggregate risks
associated with ARARs.
! Lifetime health advisories (HAs)-To be considered when evaluating human health threats from systemic toxicants in
drinking water when MCLs, proposed MCLs, State standards, or RfDs are not available.
! Maximum contaminant level goals (MCLGs) and proposed MCLGs-lf technically feasible, to be considered when other
human health threats at the site justify setting lower cleanup levels. (MCLGs may be relevant and appropriate if multiple
contaminants or multiple exposure pathways require levels that are more stringent than MCLS.)
! Water quality criteria (WQC)-To be considered for protection of aquatic organisms and for evaluating health threats from
fish ingestion and ingestion of drinking water. (Maybe relevant and appropriate, particularly if the beneficial uses of the
ground water includes any association with a surface water body or when there are not more recently adopted
health-based criteria or guidelines.)
information in IRIS can be found in the Integrated Risk
Information System (U.S. EPA, 19871). Information needed for
selecting indicator chemicals and other agency standards and
guidelines is described in the Superfund Public Health
Evaluation Manual (U.S. EPA, 1986f), which has a data base
format called the Public Health Review and Evaluation
Database (PHRED). PHRED is available from the Toxics
Integration Branch, OERR.
4.3 Derivation of Chemical-Specific ARARS
and TBCs
Two kinds of standards are considered ARARs for remediation
of ground water that is current or potential drinking water when
they are available: MCLs and promulgated State standards.
RSDs, RfDs, and HAs may be TBCs. As discussed
previously, in some cases WQC and MCLGs may be relevant
and appropriate. Unlike ARARs, which are established
through the rulemaking process, TBCs must be defended on
their merits if they are challenged during public comment;
therefore, they should be supported with thorough
documentation.
4.3.1 Maximum Contaminant Levels
MCLs are enforceable standards set for public water supply
systems promulgated under the SDWA. Generally, they are
relevant and appropriate for ground water that is a current or
potential source of drinking water, but are applicable at the
drinking water
tap if there are at least 25 users or 15 service connections to
a public water supply system.
MCLs are set at levels that are determined to be protective
and are as close as practicable to the MCLGs; but, in
addition, the MCL must account for the use of the best
available technology, cost, and other considerations.
Currently, MCLs have been established for eight organic
compounds, six pesticides, and eight inorganics. MCLs that
have been proposed in the Federal Register but are not yet
promulgated will become potential ARARs when they are
promulgated; therefore, they should be considered carefully.
Approximately 40 MCLs were proposed in the Federal
Register in 1988; these are noted in Appendix E.
4.3.2 Promulgated State Standards
Promulgated State standards are laws and regulations that
are of general applicability and are legally enforceable. State
advisories, guidances, or other nonbinding guidelines, as well
as standards that are not of general applicability, are not
considered ARARs. That is, State requirements that are
promulgated specifically for one or more Superfund sites are
not of general applicability and are not ARARs.
General State goals that are promulgated may be ARARs. For
example, a State antidegradation statute that prohibits
degradation of surface waters below specific levels of quality
or in ways that preclude certain uses of that water may be an
ARAR. A
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Dotofmlofl HI and
Adjust Cleanup
Uvctc,
If Necessary
Th«
RID Should Bt
Considered
Note: This Process Shot*! be Performed
in Corf unction wfth the RtsK Assessment
That** Cwnpteisd lor tw Sit*
Figure 4-1 Flow Chart for Determing Site-Specific Cleanup Levels on the Basis of Existing Standards and Criteria.
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MCLsFOR
CARCINOGENS
Chronic
Study
V
(kgday/mg)
Risk Level
(e.g.,1ffe)
>t.
RSD
(mg/kgday)
>.
Concentration
Associated with
Risk Level
(mg/l)
2 Way
70kg
Technical
MCLG
(0)
(mg/l)
MCL
(mg/l)
Safety
HAS FOR SHORT-TERM
AND LONGER-TERM
EXPOSURES FOR
SYSTEMIC TOXICANTS
Acute
orSubchronic
Study
NOAEL
or
LOAEL
(mg/kgday)
>,
1-Day HA
10-Day HA
Longer-Term HA
(mg/day)
LIFETIME HAS
FOR SYSTEMIC
TOXICANTS
AND SOME
GROUP C ^
CARCINOGENS , , NOAEL
Chronic ^ or
Study f LOAEL "
f>
*ty
v RfO DWEL
^(mg/kgday) *" (mg/da)
2 I/day I
7H Itn I
9 [^
Group C
Carcinogens
n
Systemic
Toxicants
>
t
-
Safety
Factor
\ ^ Uf^e ^ MCLG ^ MCL
^ * (mX) (ma^ (m9/"
Tecftreca/
Practfcabrf/fy
WQC
Bloconcentratiorf
, Factor
2 I/day
70kg
6.5gof
Fish/Day
WQC*
(mg/l)
Drinking
Water Plus
Fish
Ingestion
"WQC are also developed to reflect fish ingestion alone and have been calculated to reflect drinking water alone in the
Superfund Public Health Evaluation Manual (U.S. EPA, 1986). WQC are also developed for effects to aquatic organisms.
Figure 4-2 Derivation of Some Standard* and Heafth-Based Criteria.
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general prohibition against discharges to surface waters of
toxic materials in toxic amounts also may be an ARAR.
Because the scope of these goals is general, compliance
must be interpreted within the context of specific regulations
designed to implement them, the specific circumstances at
the site, and the remedial alternatives being considered.
A waiver from complying with State standards that are
inconsistently applied can be invoked (see Chapter 6).
4.3.3 Risk-Specific Doses for Carcinogens
Cancer potency factors are developed by the EPA Carcinogen
Assessment Group (CAG) and the EPA Environmental Criteria
and Assessment Office in a series of health effects
assessment documents. Cancer potency factors are also
referred to as slope factors or oj*, and can be found in the
IRIS data base. RSDs are determined by dividing the selected
risk level (e.g., 10~6) by the cancer potency factors. They
represent the dose of chemical in mg per kg of body weight
per day associated with the specific risk level used. To
calculate the concentration of a carcinogen in ground water
associated with a selected cancer risk level, the following
equation is used:
Cone. (Mg/l) =
RSD (mg/kg day) x body weight
drinking water injestion rate (I/day)
Body weight for the average adult is generally assumed to be
70 kg, and the drinking water ingestion rate is generally
assumed to be 2 liters per day.
As stated, for carcinogens, cleanup levels should reduce
aggregate risks to within the 10~4 to 10~7 range, and the 10~6
risk level should be used as a starting point.
4.3.4 Reference Doses
RfDs are derived from extensive analysis of toxicological data
by an Agency review group headed by representatives from
the Office of Research and Development. RfDs can be found
in the IRIS data base, along with discussions on the
strengths and limitations of each chemical's information base.
The RfD is an estimate of the daily exposure to the human
population (including sensitive subgroups) that is likely to be
without appreciable risk of adverse effects during a lifetime. It
is expressed in units of mg per kg body weight per day. RfDs
are derived from toxicological no-observed-effects levels
(NOELs), no-observed-adverse-effects levels (NOAELs),
lowest-observed-effects level (LOELs), or lowest- observed-
adverse-effects levels (LOAELs), using uncertainty factors that
account for interspecies and intraspecies diversity and the
quality of the experimental data. The NOAEL is the highest
concentration of chemical that, when administered to
a test animal, does not cause an adverse health effect, while
the LOAEL is the lowest concentration that, when
administered to a test animal, does cause an adverse health
effect. NOEL and LOEL are analogous to NOAEL and LOAEL,
respectively, but take into consideration any health effect, not
just adverse effects.
DWELs are calculated from RfDs and are determined on the
basis of medium-specific lifetime exposure levels, assuming
100 percent exposure from that medium. At the level of the
DWEL, noncarcinogenic health effects would not be expected
to occur. To obtain a ground-water DWEL, the following
equation should be used:
DWEL (mg/l) =
RfD (mg/kg day) body weight (kg)
drinking water ingestion rate (I/day)
Body weight for the average adult is assumed to be 70 kg,
and the drinking water ingestion rate is assumed to be 2 liters
per day.
4.3.5 Health Advisories
HAs are nonenforceable contaminant limits published by the
Office of Drinking Water for 1-day, 10-day, longer-term
(usually 7 years), and lifetime exposures to chemicals. HAs
are generally published for noncarcinogenic endpoints of
toxicity. Lifetime HAs are not recommended for Group A and
Group B carcinogens, because carcinogenic effects are
expected to result in more stringent health standards. For
Group C carcinogens, lifetime HAs are based on
noncarcinogenic endpoints of toxicity. An additional
uncertainty factor of 10 is used when determining the lifetime
HA to reflect possible carcinogenic effects. When determining
cleanup levels for Group C carcinogens, the more stringent of
the HA and the level corresponding to the 10"6 cancer risk
should be used, if available.
Lifetime HAs are derived from DWELs by incorporating known
exposure to contaminants from sources other than drinking
water, such as diet. (However, exposure from inhalation of
contaminants from showering for example, is not incorporated
into HAs.) HAs have been published for pesticides, inorganic
chemicals, and organic compounds (U.S. EPA, 1987f).
4.3.6 Maximum Contaminant Level Goals
MCLGs, established under the SDWA (40 CFR 141), are set,
with a margin of safety, at levels that would result in no known
or anticipated adverse effects to health over a lifetime. MCLGs
for Group A and Group B carcinogens are set at zero. MCLGs
for Group C carcinogens are either set at zero or at the
lifetime HA, depending on available information. For
noncarcinogens, the MCLG generally corresponds to
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the lifetime HA. Proposed MCLGs may also be considered
when establishing cleanup levels. In cases where multiple
contaminants or multiple exposure pathways lead to very high
risks, MCLGs may be relevant and appropriate.
4.3.7 Water Quality Criteria
WQC are established for evaluating toxic effects on human
health and aquatic organisms. Values reflecting risk levels of
10"5, 10"6, and 10"7 are published for carcinogens. WQC are
also published for noncarcinogenic (chronic toxic) effects.
WQC are determined for the following exposure settings:
! Human exposure from ingestion of contaminated
drinking water and contaminated fish
! Human exposure from ingestion of contaminated fish
alone
In addition, WQC are used to derive criteria for human
exposure from ingestion of contaminated drinking water alone
in the Superfund Public Health Evaluation Manual (U.S. EPA,
1986e).
The final values of WQC that protect human health may differ
from MCLs because WQC take into consideration a
bioconcentration factor and fish ingestion factor, while MCLs
take into consideration economic and treatability factors.
Also, many WQC have not recently been updated.
If the contaminated water is a drinking water source, MCLs
are generally an ARAR. However, if there is no MCL or if the
ground water discharges to surface water and contaminants
are affecting aquatic organisms, or if other health-based
standards are not available, WQC should be consulted and
may be relevant and appropriate. Because WQC do not
incorporate such factors as detection limits, technical
feasibility of achieving standards, or cost, the cleanup levels
for a site may have to be adjusted from the WQC value. The
WQC Standards Handbook (U.S. EPA, 1983) describes
factors to consider when using WQC and when determining
cleanup levels that are based on WQC.
4.4 Assessment of Aggregate Effects
The aggregate effects from contaminants at a site for a
particular medium, in this case ground water, generally should
be determined, using methods described in the "Guidance for
Health Risk Assessment of Chemical Mixtures," (U.S. EPA,
1986a).
Generally, both carcinogenic risks and risks from systemic
toxicants are assumed to be additive. For example, the
aggregate risk posed by all of the carcinogens in an exposure
pathway is assumed to
be the sum of the risks from the individual carcinogens.
For carcinogens (including Class C carcinogens), aggregate
risk levels calculated from cleanup levels should fall within the
10~4to 10~7 risk range. The 10~6 aggregate excess lifetime
cancer risk level is considered the starting point for analysis,
but other risk levels between 10~4 and 10~7 may be supported
on the basis of other factors such as exposure, technical
limitations, and uncertainties. If cleanup levels based on
ARARs and TBCs result in an aggregate risk level that falls
outside the protective risk range, then cleanup levels should
be more stringent than the ARARs or TBCs. Setting cleanup
levels within the risk range and ensuring that these levels at
least meet ARARs will assure that adequately protective
cleanup levels are set.
Effect levels from systemic toxicants may be added when
they act by the same mechanisms of would otherwise
magnify the toxic effect. To add effect levels from systemic
toxicants, the hazard index (HI) is used. The HI is calculated
using the equation:
ar-
DI. I RfD.
i ' i
where i = chemical i in the mixture, and Dlj = daily intake of
the chemical in mg/kg-day.
Initially, the HI should be determined from daily intakes on the
basis of cleanup levels for all systemic toxicants as a
screening approach as described in the Superfund Public
Health Evaluation Manual (U.S. EPA, 1986f). If the HI exceeds
or is close to 1.0, chemicals should be segregated by
mechanism of action and separate His should be calculated
for each group of chemicals. Cleanup levels may need to be
lowered if segregating chemicals does not reduce the HI to
below 1.0, however.
Exhibit 4-1 is an example of setting cleanup levels.
Table 4-2 describes factors that should be analyzed to
determine the most appropriate aggregate risk level. The
analysis of these factors is not quantitative but is merely a
qualitative indication of the appropriate level within the
protective risk range at which a remedy should be designed to
perform. The factors that are presented in this table highlight
considerations that may be pertinent to particular sites and
need not be addressed in every case. Although listed as a
separate factor in Table 4-2, detection limits should not be
the sole factor for deviating from the starting point, such as
the 10'6 cancer risk level, unless special analytical services
have been investigated and it is technically infeasible to detect
the chemical at the desired concentration.
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Exhibit 4-1. Setting Cleanup Levels at Seymour Recycling
The Seymour Recycling site, located in Seymour, Indiana, is situated on 14 acres in an agricultural area 1/2 mile south of a
subdivision. Waste management activities at the site began in the 1970s and included processing, storing, and incinerating
chemical wastes. Surface contamination from 50,000 drums and 100 storage tanks has resulted. Groundwater contamination
of the shallow aquifer is extensive, and a contaminant plume extends 1,100 feet from the site boundary. The deeper aquifer,
which is separated from the shallow aquifer by a silty clay aquitard, has very limited contamination.
More than 35 hazardous organic chemicals have been detected in ground water, including 1,2-dichloroethene, benzene, vinyl
chloride, and 1,1,1-trichloroethane. Ten carcinogens and 12 noncarcinogens with critical toxicity values have been identified in
ground water at the site.
Establishment of Cleanup Levels
For carcinogens with MCLs, the cleanup levels were stricter than the MCLs because of the aggregate effects of the
contaminants. The aggregate risk of the six organic carcinogens detected at the site which have MCLs is 4 x 10"4 at the MCL
levels. An aggregate excess cancer risk of 1 x 10"5was selected as the ground-water cleanup level for carcinogens. This risk
level was selected because there are a large number of ground-water contaminants, because there is limited understanding of
the contaminants' aggregate effect, because low levels of contaminants will continue to migrate when the extraction system is
terminated, and because the aquifer is a potential source of drinking water. A 1 x 10"6 risk level must be met at the site's nearest
receptor. In addition to meeting the 1 x 10~5 aggregate risk level, the individual MCLs must be met throughout the aquifer. The
compounds used for setting the aggregate excess cancer risk for the site were:
Benzene
Methylene chloride
Chloroform
Tetrachloroethane
1,2-Dichloroethane
1,1,2-Trichloroethane
1, 1-Dichloroethene
Trichloroethene
1,4-Dioxane
Vinyl chloride
This list will be revised if other chemicals that are carcinogenic by the oral route of exposure are identified or if other compounds
are identified as possible, probable, or known human carcinogens.
For noncarcinogens, the total hazard index (HI) for all compounds for which there is a reference dose (RFD) will not exceed 1.0.
These compounds include the following:
Barium
2-Butanone
Copper
2-Methylphenol
4-Methylphenol
1,1-Dichloroethane
Manganese
Methylene chloride
Nickel
Phenol
Toluene
Zinc
In addition, for those compounds for which there is an MCL, the MCL will not be exceeded. The list shall be updated as additional
RfDs or other information becomes available and as MCLs are established for additional compounds.
The information needed to evaluate many of these factors is
often included in the risk assessment for a site. In addition,
information gained during implementation of an interim action
may be useful for evaluating these factors.
4.5 Alternate Concentration Limits
Section (121)(d)(2)(B)(ii) of CERCLA restricts the use of ACLs
for offsite exposure in the selection of a remedial action in lieu
of otherwise applicable
limitations. ACLs can only be used as cleanup levels at the
end of the remedial action and only if the following conditions
are met:
! The ground water has known or projected points of
entry into surface water, which is a reasonable
distance from the facility boundary.
! There will be no statistically significant increase at
the 95 percent confidence level of constituent
concentrations occurring in the surface water in
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Table 4-2. Factors Considered When Determining Preliminary Cleanup Levels
Factors Related
to Exposure
Timing of exposure
The potential for
human exposure
from other
pathways
Population
sensitivities
Potential effects on
environmental
receptors
Cross-media
effects of
alternatives
If data demonstrate that exposures are occurring continuously, more stringent cleanup levels may
be warranted than if exposures were projected or the probability of exposure is low.
If a site presents a threat from contaminants from two or more media or pathways (e.g, soil and
ground-water exposure) and there is a potential for exposure from multiple media, more stringent
cleanup levels may be warranted because of the potential for higher exposure.
The current risk borne by the population may be substantial enough to warrant a more stringent
cleanup level for a contaminant in ground water. If the site is near a school where the potential
for children to be exposed is higher than normal, then more stringent cleanup levels may be
appropriate, through this is accounted for to some extent during development of standards and
health-based criteria, which takes into account sensitive individuals.
The presence of a particular plant or animal species near the site may warrant a more stringent
cleanup level.
A remedy that achieves an acceptable risk level in one medium may not be preferred if it only
achieves this level by transferring contaminants to another medium at an unacceptable risk level.
Factors Related
to Uncertainty
Effectiveness and
reliability of
alternatives
Reliability of
exposure data
Reliability of
scientific evidence
A remedy that has been demonstrated to be effective and reliable at sites that are similar may be
chosen over a remedy that might reach a more protective level under ideal conditions but is
undemonstrated for the conditions of a particular site. If a remedy with a low degree of certainty
of attaining cleanup levels is chosen, the system could be designed to meet more stringent
cleanup levels to increase the probability that the remedy will fall within the protective risk range;
thus providing an additional measure of safety. Also, the reliability of any institutional controls that
are part of the alternative should be considered.
If exposures are actually occurring, more stringent cleanup levels may be warranted than if
exposures are only predicted to occur using transport modeling. Less stringent cleanup levels
may be warranted when exposure is expected to be intermittent
A contaminant that is a known human carcinogen may require a more stringent cleanup level than
a contaminant for which there is weak evidence of carcinogenicity. The weight of evidence with
respect to severity of effect should also be considered.
Factors Related
to Technical
Limitations
Detection/quantifi-
cation limits for
contaminants
Technical
limitations to
restoration
Background levels
If standard laboratory procedures can only detect contaminants at concentrations reflecting the
10"4 risklevel, for example, then that level may be appropriate. However, in some situations, such
as when the quantification limit is higher than the cleanup level, it may be appropriate to use
special analytical methods to achieve lower quantification limits. (This should not be the sole
criterion for deviating from cleanup levels.)
If remediation is technically limited because of site hydrogeological characteristics, the nature of
the soil matrix, or difficulties associated with treatment of a particular contaminant, more stringent
cleanup levels may not be feasible. In addition, if the ability to monitor and control the movement
of contaminants is technically limited, such as in karst aquifers, highly varied alluvial deposits, or
with dense nonaqueous phase liquids, it may be difficult to monitor the actual reduction achieved.
Cleanup levels lower than background levels are not, in general, practicable; e.g., if the
background level of a particular contaminant is at the 10"4 risk level, a more stringent cleanup level
is not practicable. However, if background levels are above ARARs and the ground water is a
drinking water source, it may be appropriate to initiate a coordinated response with other
agencies. If background levels are high because of natural sources, well-head treatment may be
the most effective solution, although such ground water is probably not a drinking water supply.
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the discharge zone or at any point where constituents
are expected to accumulate.
! Institutional controls will be implemented that will
preclude human exposure to ground-water
contaminants between the facility boundary and the
point of entry into the surface water.
In addition, ACLs should only be developed under this
provision when remediating to drinking water levels is not
practicable. Furthermore, ACLs should be used only if there
is no significant degradation of uncontaminated ground water
before discharge to surface water occurs. Exhibit 4-2 presents
an example of using ACLs.
Determining statistically significant increases of constituent
concentrations in surface water should include the following
steps as appropriate:
! Samples of surface water should be taken during a
period in which the flow (for rivers and streams) or
standing volume (for ponds and lakes) is near base
flow conditions for the specific season. Stream width
and depth should also be considered.
! Surface water samples should be collected within the
discharge zone of the ground-water contaminant
plume. Because ground-water movement nearsurface
water bodies can be complex, initial samples may
have to be collected adjacent to the facility as well as
some distance downstream to identify the discharge
zone.
! Sediment and biota samples should be collected
when surface water samples are collected to
determine if contaminants are accumulating in the
sediments or biota.
! Contaminant degradation should be considered, and
analysis for potential degradation products should be
conducted.
! If concentrations of contaminants in shallow and deep
ground water adjecent to the surface-water body are
not detectable, this statistical determination need not
be performed. If the levels are detectable, then
concentrations in the discharge zone should be
compared to concentrations in a background area of
the surface-water body.
! If concentrations of contaminants are found in the
deeper aquifer, then samples should be taken
downstream.
! If ACLs are established for a site, periodic surface
water sampling should be conducted
4.6 Summary
When establishing preliminary cleanup levels, the following
steps should be taken:
! Identify ARARs and associated risk levels for
carcinogen and daily intake values for systemic
toxicants
! Identify TBCs for contaminants for which ARARs are
not available (it may also be important to identify
TBCs for contaminants with ARARs in order to
calculate aggregate risks or evaluate impacts, such
as environmental effects, not addressed by ARARs)
! Assess aggregate risk in the ground water and
determine the appropriate risk level (carcinogens) or
HI (systemic toxicants)
! If it is not practicable to attain applicable
requirements and site condition permits, consider
establishing ACLs and using institutional controls, if
necessary, to restrict site access
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Exhibit 4-2. Ground Water Discharging to Surface Water
The Newport Dump site is a 39-acre former municipal landfill in Wilder, Kentucky, that lies on the Licking River, a tributary of
the Ohio River. Approximately 250 feet downstream of the site is the main water intake for a water treatment plant. The plant
withdraws up to 18mgdfrom the Licking River and serves about 75,000 people. The site was used by the city for the disposal
of residential and com mercial wastes from the 1940s until its closure in 1979.
The major concern at the site is leachate migration to a nearby unnamed stream forming the southern border of the site and
to the Licking River. The surface water contaminant migration pathway was examined by collecting surface water and sediment
samples at six locations in the stream and five nearshore locations in the Licking River. Many of these sampling points were
also paired with shallow ground-water sampling points to evaluate the potential ground-water distribution to surface water.
Shallow ground water, which discharges to the Licking River, was sampled and contained metals, solvents, and polycyclic
aromatic hydrocarbons. Samples of the deeper ground water were clean.
Surface water and sediment samples were collected from the stream and the river, and two samples were taken at the
surface-water intake. The results of the chemical analyses demonstrated that the levels of contaminants in the stream were
below all detectable levels except for toluene, which was detected in upstream samples as well as downstream samples.
Ground-water dilution by the Licking River was calculated to be over 40,000 to 1 under low flow conditions. Thus, it was
concluded that site contaminants did not have any effect on the quality of the Licking River.
The main receptors for contaminant releases from the site are the 75,000 residents served by the water intake. Approximately,
1,200 individuals live within a 1-mile radius of the site, but no private or public drinking water wells were found within this area.
The potential receptors include those people who eat fish caught from the Licking River. Currently, there is no recreational use
of the site, though the site has uncontrolled access. The risk assessment found no evidence of any current public health or
environmental concerns associated with the site. It was therefore concluded that the principal human exposure point
associated with the site is the withdrawal of surface water from the intake on the Licking River.
Currently, no data exist that demonstrate that contaminants detected onsite are increasing contaminant levels in the Licking
River. Of the seven indicator chemicals used, only toluene was detected in a raw water sample collected at the intake.
However, toluene was also detected in higher concentration in a background sample; therefore, there was no increase in
concentration as a result of the site. Ground-water remediation between the landfill and the Licking River is not practicable
because (1) concentrations of contaminants are low, (2) ground-water flow to the river is relatively low, and (3) the cost of
remediation is high. Consequently, ACLs, as defined in Section 121 (d)(2)(B)(ii) of CERCLA, were developed. They are
presented below:
Actual and Projected
Concentration Levels
Indicator
Chemicals
Arsenic
Barium
Chromium
Nickel
Toluene
Ground-Water
Concentration,
mg/l
0.064
7.4
1.5
2.4
0.017
Proposed
ACL, mg/l1
0.64
74
15
24
0.17
Standard or
Health-Based
Criteria,
mg/l
0.05 (MCL)
1 (MCL)
0.05 (MCL)
0.13(WQC)
0.14(WQC)
Projected
Concentration
in the
Licking River,
mg/l
1.6x10-6
1.9x10-4
3.8 x10'3
6.0x10-5
4.2 x10'3
1These concentrations are ten times the level of ground-water contamination.
The proposed ACLs are based on actual ground-water contamination levels. At the ACL levels, concentrations projected in the Licking
River will be below all existing health and environmental standards and criteria. Therefore, they represent a protective baseline limit for
deciding if any future remedial action will be necessary.
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Chapter 5
Developing Remedial Alternatives
5.1 Introduction
This chapter describes how remedial alternatives are
developed. Developing remedial alternatives occurs when
enough site information has been obtained to identify
appropriate operable units or final remedies. If necessary,
alternatives are screened on the basis of general
considerations of effectiveness, implementability, and cost to
reduce the number of remedial alternatives considered in the
detailed analysis.
Detailed guidance on the development of alternatives is
provided in Chapter 4 of the RI/FS Guidance (U.S. EPA,
1988c). This chapter presents additional information for
developing a reasonable range of remedial action alternatives
for sites with contaminated ground water.
Developing remedial action alternatives encompasses the
following steps:
! Determining remedial action objectives
- Establishing preliminary cleanup levels (see Chapter
4)
- Determining the area of attainment
- Estimating the restoration time frame
! Developing alternatives
- Determining response actions
- Determining process options
- Formulating alternatives
In actual project applications, these steps may be repeated at
various stages of the Superfund process including:
! During the Rl to assist in planning cost-effective Rl
activities
! During preliminary stages of the FS
! During detailed evaluation in the FS
This iterative approach allows for flexibility to respond to new
data and to changes in the project and should ultimately
result in a detailed evaluation of a limited number of
alternatives. The factors used to evaluate the alternatives and
select a ground-water remedy are discussed in Chapter 6 of
this guidance.
5.2 Remedial Action Objectives
Response objectives are site-specific, initial cleanup
objectives that are established on the basis of the nature and
extent of the contamination, the resources that are currently
and potentially threatened, and the potential for human and
environmental exposure. Table 5-1 presents a partial list of
remedial action objectives for contaminated ground water at
Superfund sites. While this list covers many of the situations
encountered at Superfund sites, other remedial action
objectives may be appropriate because of site-specific
conditions.
Remedial action objectives are site-specific, quantitative goals
that define the extent of cleanup required to achieve the
response objectives. They include the preliminary cleanup
levels, the area of attainment, and the restoration time frame.
Remedial action objectives are generally developed in the
initial phase of the FS and are used as the framework for
developing detailed remedial alternatives. The objectives are
formulated to achieve the overall goal of the Superfund
program to protect human health and the environment by
restoring potentially usable contaminated ground water to, and
protecting usable uncontaminated ground water at, levels that
are safe for current and potential users and environmental
receptors. The specificity of these objectives may vary
depending on the availability and quality of site information,
site conditions, and the complexity of the site.
5.2.1 Area of Attainment
The area of attainment defines the area over which cleanup
levels will be achieved in the ground water. It encompasses
the area outside the boundary of any waste remaining in place
and up to the boundary of the contaminant plume. An
example of the area of attainment is illustrated in Figure 5-1.
Usually, the
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Table 5-1. Potential Response Objectives for Ground Water
! Prevent exposure to contaminated ground water
Provide an alternate water supply for the population that has existing wells affected by the contaminant plume
Establish institutional controls to restrict access to the contaminant plume
! Protect uncontaminated ground and surface water for current and future use
Prevent contamination of existing wells that could be affected by the plume and in adjacent ground water
Minimize migration of contaminants within the ground and surface water
Minimize migration of contaminants to adjacent ground and surface water
! Restore contaminated ground water for future use
Reduce contaminant concentrations within the area of the plume to levels that are safe for drinking
! Protect environmental receptors
Reduce contaminant concentrations in the plume to levels that are safe for biological receptors that may be affected at the
ground-water discharge point.
boundary of the waste is defined by the source control
remedy. For example, if the source is removed, the entire
plume is within the area of attainment. On the other hand, if
waste is managed or contained onsite, the ground water
beneath the waste management area is not within the area of
attainment. Cleanup levels should be achieved throughout the
area of attainment.
ND
10
ND
45 Monitoring Well Location and
Contaminant Concentration
Contour of Contaminant Concentration
ND = Not Detected (Contaminants
were not detected in the samples
analyzed at these points)
Area of Attainment
5.2.2 Restoration Time Frame
The restoration time frame is defined as the period of time
required to achieve selected cleanup levels in the ground
water at all locations within the area of attainment. Factors
that can affect the choice of technologies, which in turn
affects the restoration include the following:
! Technical limits to extracting contaminantsthis factor
must be evaluated first to determine the restoration time
frame that is practicable for the site
! The feasibility of providing an alternate water supply
! The potential use and value of the ground water-
successively higher classes of ground water should be
remediated more rapidly
The effectiveness and reliability of institutional controls
The ability to monitor and control contaminant movement
These factors are explained in the following paragraphs.
Figure 5-1
Conceptural Diagram of Waste Source,
Containment Plume, and Attainment Area.
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5.2.2.1 Technical Limits to Extracting
Contaminants
The rate at which an aquifer can be restored through
extraction and treatment is affected by contaminant-soil
interactions, the nature of the contaminants, and the physical
conditions of the site and contaminant plume. For all
chemicals present in the ground water there is an equilibrium
between the amount of the chemical that is sorbed to the
aquifer material and the amount dissolved in the ground water.
The rate at which the chemical desorbs as clean water
is drawn into the contaminated zone as a result of pumping
will limit the pumping rate that can effectively remove the
contaminants. As discussed in Chapter 3, in many cases
this rate can be estimated by calculating partition coefficients
for the contaminants using saturated soil core analyses and
incorporating this information into models to estimate the
restoration time frame.
The presence of dense nonaqueous phase liquids (DNAPLs)
also may affect the extent to which contaminants can be
removed from the ground water; points of accumulation are
difficult to identify, and unless the well screen is located in the
nonaqueous liquid phase, the contaminant will only be
extracted slowly as it dissolves into the ground water.
Naturally, the nature of the source, the size of the plume, and
the transmissivity of the aquifer also will directly affect the
restoration time frame. For example, leaching of contaminants
from large areas contaminated at low concentrations or from
non-homogeneous fills with undetermined hot spots may
continue to affect the ground water and should be accounted
for to the extent possible in estimating the restoration time
frame. Estimating the restoration time frame will be difficult if
the site is not adequately characterized during the Rl; it will
be especially difficult if the action to address the source has
not yet been determined.
Models can be used as a tool to estimate the restoration time
frame feasible for the site, accounting for site-specific factors,
as described in Chapter 3 and exemplified in Exhibit 3-5.
Once technical limits to extracting contaminants have been
assessed, restoration time frames for remedies can be
evaluated relative to this limit.
5.2.2.2 Feasibility of Providing an Alternate Water
Supply
For sites at which ground-water users are currently or
potentially affected by the continued migration of a
contaminant plume before remedial measures are likely to be
effective, the feasibility of providing an alternate water supply
during the remedial action and the characteristics of any
potential alternate water
sources should be evaluated. The following issues should be
addressed:
! The time and cost required to develop an alternate water
supply
i
The quality of the alternate water supply
! The reliability of the alternate water supply, particularly
in terms of susceptibility to contamination
! The sustainable quantity, or safe yield, of the water
supply, considering the water use demands of those
current users affected by the site, any current or
potential competing demands, as well as any water
rights issues
! Whether the alternate water supply is itself irreplaceable
(i.e., is there a backup to the alternate source)
A readily accessible water supply of sufficient quality and
yield that is protected from sources of contamination may
reduce the importance of rapid remediation, providing more
flexibility to select a response action that requires a longer
time to achieve the cleanup level. The presence of a backup
source to the alternate water supply adds substantially to the
reliability of an alternate supply.
5.2.2.3 The potential Use and Value of the
Ground Water
If ground water contaminated from a Superfund site is not
currently used but is a potential source of drinking water
(Class MB), the potential need should be evaluated in terms of
the following:
! Timing, i.e., when a demand for the ground water is
anticipated
! The magnitude of the potential need, i.e., volume per day
! The type of need, e.g., drinking water, irrigation,
manufacturing, etc.
! The availability and characteristics of other water
sources in the same area
If a demand for high-quality ground water (e.g., drinking water)
is anticipated in the near future and other potential sources
are either not available or are of insufficient quality or quantity,
remedial alternatives that rapidly achieve cleanup levels are
preferred.
Predicting potential need is difficult. Reasonable assumptions
on type, timing, and volume of potential need for the
contaminated ground water should be made to guide
decisions concerning the restoration time frame.
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5.2.2.4 Effectiveness and Reliability of
Institutional Controls
Institutional controls implemented at the State or local level
that restrict ground-water use should beimplemented as part
of the response action at all sites at which exposure poses a
threat to human health. In addition, institutional controls may
be used to prohibit offsite extraction of ground water if
extraction would increase contaminant migration.
The following kinds of institutional controls have been
established in some states and localities and may be
considered to prevent exposure to contaminated ground water:
! Regulatory restrictions on construction and use of private
water wells, such as well construction permits and water
quality certifications
! Acquisition of real property by the government from
private entities (acquisition must be exercised in
accordance with EPA Delegation 14-30; concurrence by
EPA headquarters is required)
! Exercise of regulatory and police powers by
governments, such as zoning and issuance of
administrative orders
! Restrictions on property transactions, including negative
covenants and easements
! Nonenforceable controls, such as well-use advisories
and deed notices
Property ownership may allow extension of the restoration
time frame but does not alleviate responsibility for achieving
cleanup levels throughout the area of attainment. For new
ground-water users, licensing of well drillers, well construction
permits, well construction and location standards, and water
quality certification programs are generally effective, as are
regulations of new development and property transactions.
However, the institutional control cannot be deemed effective
without considering the specific circumstances; it depends on
the specific site, the State and local authorities, and any
private parties that are involved. Zoning could also be used,
though it is generally the jurisdiction of the local planning or
zoning board.
For existing ground-water users, advisories could be issued,
but their reliability generally is limited. Administrative orders
also could be issued.
The effectiveness and reliability of these controls should be
evaluated when determining whether rapid remediation is
warranted. If there is adequate certainty that institutional
controls will be effective and reliable, there is more flexibility
to select a response action that has a longer restoration time
frame.
Conversely, if it is unclear that an authority will establish
institutional controls, or that an effective and reliable
enforcement mechanism is in effect, emphasis should be
placed on response actions that more rapidly restore the
ground water. Institutional controls should be monitored
periodically to ensure the effectiveness of the response
actions. Exhibit 5-1 is an example of institutional controls
used by the State of New Jersey.
5.2.2.5 Ability to Monitor and Control
Contaminant Movement
Complex flow patterns may reduce the effectiveness of a
remedial action. The ability to monitor and control the
movement of contaminants in ground water depends on the
properties and volume of the contaminants, the complexity of
the hydrogeology, and the quality of the hydrogeologic
investigation. If the hydrogeology is relatively simple and the
ground-water flow paths and the distribution of contaminants
in the ground water are well characterized, predictions of
remedial action performance are more reliable. This increased
reliability provides greater flexibility to select a remedial
alternative that requires more time to achieve cleanup levels.
If flow patterns are complex and the hydrogeologic system is
difficult to characterize, the potential for unanticipated
migration pathways to develop increases, which may reduce
the effectiveness of the remedial action. Remedial actions
should be designed to prevent, as quickly as possible and to
the extent practicable, further spread of a plume in these
complex systems. However, some hydrogeologic systems,
such as mature karst areas and areas with fractured bedrock,
may make remediation of ground water impracticable.
5.3 General Response Actions
After developing cleanup levels and other remedial action
objectives, response actions that are consistent with the
remedial action objectives are identified. Categories of general
response actions for contaminated ground water include active
restoration, containment through hydraulic control, and limited
or no active response. These actions should be combined, if
appropriate, with institutional controls to protect human health
until such time that contaminants in ground water have been
reduced to a level that is safe for consumption. The
application of these general response actions is discussed
below.
5.3.1 Active Restoration
Active restoration usually reduces ground-water contaminant
levels more rapidly than plume containment or natural
attenuation. Factors that
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Table 5-1. Institutional Controls in New Jersey
New Jersey has implemented its authority to regulate access to contaminated ground water for the purpose of protecting public health.
The state has delineated the boundaries of 19 areas where ground-water supplies are not potable because of chemical contaminants.
The authority under which the New Jersey Department of Environmental Protection (DEP) makes these designations is a State statute
that requires well drillers to secure a permit before constructing any ground-water wells. These designated areas have been
established by the DEP on the basis of well sampling and other data obtained by DEP geologists. The Bureau of Water Supply issues
restrictions for two types of areas:
! Those areas in which wells are contaminated or are likely to become contaminated within 2 to 3 years without remedial
action
! Those areas in which wells are likely to become contaminated within 10 years without remedial action
The DEP's practice is to deny any well permit application to construct a private well in any restricted area.
The DEP has been given the authority to issue or deny a well-construction permit. On the basis of the DEP's own interpretation, it either
(1) denies or (2) conditionally approves permit applications in those areas that have been designated as well -restriction areas. The
DEP has not issued regulations governing practices and procedures for reviewing well-construction permits but was scheduled to
propose and adopt such regulations in late 1986. It is expected that the regulations will include a section on permit denials, with
language to the effect that "reasons for denying a permit include...the site where the well is planned has been designated by DEP
as an area where wells cannot be constructed."
Well drillers apply for construction permits on forms provided by the DEP. It is at this stage that DEP screens out applications for wells
from the restricted areas. The DEP generally denies those permits on the basis of the formal designation. However, sometimes
applications for wells in the restricted areas are reviewed by DEP geologists for alternative construction methods. In some cases, the
driller has been allowed to proceed with well construction on the condition that the well be drilled into a deeper, uncontaminated aquifer
and that the driller conform to special construction procedures, i.e., casing the upper aquifer to prevent cross contamination. Although
there is no surveillance or enforcement of the permitting requirements, officials in charge of the program state that it is successful.
potentially favor the use of active restoration include:
! Mobile contaminants
! Moderate to high hydraulic conductivities in the
contaminated aquifer
! Effective treatment technologies
contaminants in the ground water
available for the
5.3.1.1 Extraction and Treatment
An extraction system can be used to remove contaminated
ground water. This is followed by treatment, if required, and
discharge or reinjection back into the aquifer. Extraction can
be achieved by using pumping wells, French drains, or
trenches. Pumping may be continuous or pulsed to remove
contaminants after they have been given time to desorb from
the aquifer material and equilibrate with ground water.
Treatment may involve air-stripping, carbon adsorption, and
biological treatment, depending on the physical/chemical
properties of the contaminants.
5.3.1.2 Innovative Technologies
Because extraction and treatment systems may not be able
to remediate ground water to health-based levels in a
reasonable time frame for some contaminants or in some
zones where contaminants have saturated the aquifer
material, innovative methods may be considered alone or in
conjunction
with extraction to reduce contaminants below the level at
which they have reached equilibrium with the saturated soil
and to treat or contain the source of contamination. Methods
that are in the developmental stage for ground water treatment
and source control include biorestoration, soil flushing, steam
stripping, ground-water pumping in conjunction with soil
vacuum extraction, and in situ vitrification. These technologies
are briefly described in the following paragraphs. The fact that
most in situ technologies require extensive pilot testing to
ensure their viability at a particular site should be considered
during the RI/FS.
Biorestoration relies on microorganisms to transform
hazardous compounds into innocuous materials. Almost all
organic compounds and some inorganic compounds can be
degraded biologically if given the proper physical and chemical
conditions and sufficient time. Biological processes are
particularly useful for detoxifying aqueous solutions containing
dilute concentrations of hazardous materials. Biorestoration
can be enhanced by using the native microorganisms and
injecting nutrients, including oxygen, or by injecting
microorganisms to the subsurface environment. Some organic
compounds readily biodegrade, while other molecules degrade
at a much slower rate. Some organic compounds are toxic to
microorganisms or inhibit their activity. Special methods may
be necessary to enhance biorestoration
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of these compounds. The toxicity of degradation by-products
should also be considered. In some cases, such as with the
degradation of trichloroethylene to vinyl chloride, the
by-products are more toxic than the parent compound. Exhibit
5-2 presents an example of the use of bio restoration at a
pharmaceutical plant.
Soil flushing refers to applying a liquid flushing agent to
contaminated soil to physically or chemically remove
contaminants. The flushing agent is allowed to percolate into
the soil and enhance the transport of contaminants to
ground-water extraction wells for recovery. The extracted
solvent may then be treated and recycled. Water is normally
used as the flushing agent; however, other solvents may be
used for contaminants that are tightly held or only slightly
soluble in water. Solvents are selected on the basis of (1) their
ability to solubilize the contaminants and (2) their
environmental and human health effects. Thus, it is important
to know the chemistry and toxicity of the surfactant. It is also
important to understand the hydrogeology of the site to ensure
that contaminants will be extracted once they are mobilized.
This technology is most applicable for soluble organics and
metals at a low-to-medium concentration that are distributed
over a wide area. This technology can reduce the time
required to complete ground-water cleanup.
In situ steam stripping is an innovative technology used to
enhance the volatilization of organic compounds in the soil.
Steam is injected and mixed into the ground through specially
adapted hollow core drill stems. Volatilized organic
compounds rise to the surface and are collected via a blower
system. The collected gases are treated to condense the
organics and trap the remainder on activated carbon. Once
treated, the gases are reheated and reinjected. This
technology allows fora high degree of organics to be removed
in a relatively short time.
Soil vapor extraction has been used at several sites to
augment ground-water extraction and treatment. This
technology can be applied using a variety of system designs,
depending on site conditions. A vacuum is applied to
subsurface soils in the unsaturated zone and in dewatered
portions of the saturated zone. The extracted vapor or soil gas
contains volatile contaminants that can be either vented
directly to the atmosphere or collected in a vapor-phase
carbon adsorption system. This system may consist of a
single extraction well screened in the contaminated zone, or
it may include inlet wells that direct air flow through a
particular interval. Figure 5-2 illustrates how this type of
system might be designed for a leaking underground storage
tank. At this time, no generally applicable design guidelines
can be provided because the design and operation of soil
vapor extraction is an emerging technology.
There are many factors to be considered in deciding if soil
vapor extraction should be tried, such as:
! Types of volatiles
! Concentration
! Quantity of volatiles
! Volume and depth of contaminated soil
! Depth to ground water
! Physical characteristics of the contaminated soil,
particularly stratification and permeability
! Surface of the contaminated area
Some considerations that may be useful are:
! Depth of contaminated soil-it may be more practical to
trench across the area of contamination and install
perforated piping in the trench bottom than to install
vapor extraction wells.
! Short-circuiting of air from the ground surface to the
vapor extraction intake-it may be possible to cap or
cover the surface to limit the short circuiting.
! Flow nets-model the pressure drops and flow of air
through the soil, and include provisions in the design to
enhance the flow through the areas of maximum
concern.
! Staged soil vapor extraction installation-design and
install the system in phases to maximize the
effectiveness of inlet and outlet locations.
! Air emissions-there are several ways that air emissions
can be limited and controlled (e.g., use of carbon
adsorption units).
In situ vitrification (ISV) is a thermal treatment process that
converts the contaminated area into a chemically inert, stable
glass and crystalline product. Electrodes are inserted into the
area to be treated, and a conductive mixture of flaked graphite
and glass frit is placed among the electrodes to act as the
starter path. An electric potential is applied to the electrodes,
establishing an electric current in the starter path. The
resultant power heats the starter path and surrounding
material above the fusion temperature of soil. The graphite
starter pad is consumed by oxidation, and the current is
transformed to the molten soil. As the vitrified zone grows, it
incorporates nonvolatile elements and destroys organic
compounds by pyrolysis. Any water present is vaporized. The
pyrolyzed by-products migrate to the surface of the vitrified
zone, where they combust in the presence of oxygen. A hood
placed over the processing area is used to collect the
combustion gases, which are drawn off and treated in a
separate system. The ISV technology has been demonstrated
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Exhibit 5-2. Biorestoration at Biocraft Laboratories
Biocraft Laboratories is a small synthetic penicillin manufacturing plant located on a 4-acre site in an industrial park in
Waldwick, New Jersey. Several years ago contamination was discovered in the shallow aquifer below the site. The
contamination consisted of a mixture of methylene chloride, acetone, n-butyl alcohol, and dimethyl aniline.
Biocraft evaluated several cleanup alternatives and settled on a biodegradation process. The system included the
following:
! Collecting the contaminated plume downgradient of the source in a slotted-pipe collection trench and two
interceptor wells
! Treating the collected ground water in a surface aerobic biological treatment system
! Injecting the treated water upgradient of the source in two slotted-pipe recharge trenches to flush the soil of
contaminants
! Stimulating in situ biodegradation of contaminants in the subsurface by injecting air through a series of aeration
wells along the path of ground-water flow
The system has proven to be quite effective. After 3 years of operation, the contaminant plume was reduced by
approximately 90 percent.
at full scale at sites containing PCBs, plating wastes, and
process sludges. For ground water, it is probably only
practicable for shallow, discontinuous, low-productivity zones
because of the additional energy required for vaporization.
5.3.2 Plume Containment or Gradient Control
Plume containment refers to minimizing the spread of a plume
through hydraulic gradient control, which can be either active
(e.g., by using pumping wells or French drains) or passive
(e.g., by using a slurry wall). These options rely on the
prevention of exposure for the protection of human health.
Slow contaminant removal (for gradient control systems) or
natural attenuation may gradually achieve cleanup levels
within the contained area. Conditions that potentially favor the
use of a containment alternative include:
! Ground water that is naturally unsuitable for
consumption (e.g., Class III aquifers)
! Low mobility contaminants
! Low aquifer transmissivity
! Low concentrations of contaminants
! Low potential for exposure
! Low projected demand for future use of the ground water
5.3.3 Limited or No Active Response
This category of response action includes two distinct
alternatives: (1) a natural attenuation alternative that includes
monitoring and institutional controls that should be developed
in many cases as a point of comparison; and (2) wellhead
treatment or provision of an alternate water supply with
institutional controls,
when active restoration or containment is not feasible or
practicable.
5.3.3.1 Natural Attenuation with Monitoring
Natural attenuation relies on the ground water's natural ability
to lower contaminant concentrations through physical,
chemical, and biological processes until cleanup levels are
met. Natural attenuation generally is a long-term response
action that continues until cleanup levels have been attained
throughout the area of attainment, when the site can be
removed from the National Priorities List. Natural attenuation
should be carried through the detailed analysis as a point of
comparison, but it is not generally recommended except when
active restoration is not practicable, cost-effective, or
warranted because of site-specific situations; e.g., Class III
ground water is contaminated. A natural attenuation response
action generally includes monitoring to track the direction and
rate of movement of the plume, as well as responsibility for
maintaining effective, reliable institutional controls to prevent
use of the contaminated ground water. The use of institutional
controls should not, however, substitute for active response
measures, unless such measures have been determined not
to be practicable based on the balancing of tradeoffs among
alternatives that is conducted during the selection process.
Conditions that potentially favor the use of natural attenuation
include the factors listed under Section 5.3.2, as well as
conditions appropriate under CERCLA Section 121(d)(2)(B)(ii)
(discharge to surface water). For example, when
contaminants are expected to attenuate to health-based levels
in a relatively short distance or when there is a narrow strip of
land between the discharge stream where contaminant levels
are not expected to increase,
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Contaminated
Ground-water
Figure 5-2. Schematic of a Soil Vapor Extraction System.
natural attenuation may be the most practicable response.
5.3.3.2 Special Situations Requiring Wellhead
Treatment or Alternate Water Supply and
Institutional Controls
There are special situations when it may not be practicable or
feasible to fully restore ground water. Widespread plumes,
hydrogeological constraints, contaminant-related factors, and
physical/chemical interactions may limit the effectiveness of
active restoration. Natural attenuation and well head treatment
with monitoring and institutional controls may be the only
feasible remedies for these sites. A technical impracticability
waiver from meeting an MCL in drinkable ground water may be
needed in these circumstances. If levels of contaminants are
projected to attenuate, a waiver may not be necessary if
cleanup levels will be achieved in a reasonable time frame (i.e.,
less than 100 years).
Widespread plumes that frequently cannot be remediated
feasibly can result from the following situations:
! Sites in industrial areas where shallow ground water is
easily contaminated-ln these cases, remediation may be
difficult because the ground water could easily be
recontaminated and specific point sources cannot be
identified. This does not include the case where separate
sources can be identified, which should be addressed
using the multiple source ground-water policy described
in Appendix B.
! Mining and pesticide sites-These sites have high
volumes of wastes that generally cover large areas.
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Hydrogeological constraints that can limit the effectiveness of
active restoration occur when plumes migrate into formations
from which they cannot easily be removed. Although some
level of contaminant reduction can usually be achieved,
complete restoration to health-based levels may not be
feasible. These situations include:
! Contaminant migration into fractured bedrock
! Contaminant migration into karst aquifers
! Sites at which the transmissivity of the aquifer is less
than 50 ft2/day
Contaminant-related factors include situations where the
nature of the contaminant makes restoration difficult. For
example, when DNAPLs migrate to ground water, they
frequently sink to the less permeable material at the base of
the aquifer, accumulating in isolated areas above the less
permeable material. Generally, these contaminants can only
be removed by extraction directly at the points of
accumulation, which often cannot be identified practicably. In
such cases, a remedy involving extraction wells or an
interceptor trench between the site and any drinking water
wells to collect the DNAPLs as they dissolve may be the only
feasible remedy.
Physical/chemical interactions, such as partitioning, can limit
the effectiveness of restoration. As discussed in Chapter 3,
the rate at which contaminants desorb from the aquifer
material limits the rate at which the aquifer can be restored.
Factors that influence sorption include the length of time the
contaminants have been in contact with the aquifer material
and the organic content of the soil. Sometimes the organic
content of the soil is artificially increased by the presence of
long-chain hydrocarbons in the plume.
5.4 Formulating and Screening
Alternatives
A range of remedial technologies can be combined under a
particular general response action. Figure 5-3 provides an
overview of some of the technologies available for a ground-
water remedial action. Alternatives are developed from
combinations of these various process options.
Examples of remedial alternatives include the following:
! Active resforaf/on-Three extraction wells pumping at a
rate of 10 gpm to a carbon adsorption unit and
discharging to a POTW
! Plume confa/nmenf-lnstallation of a bentonite barrier
wall and use of well construction permits to prevent new
well installation within the area of the plume
! Natural attenuation-Mor\\lor\r\g of ground water for 10
years when contaminant levels are expected to
attenuate to health-based levels
! No Active Response-Development of ACLs and
issuance of well-construction restrictions
The components that are incorporated in a remedial alternative
can include extraction, containment, treatment, discharge,
and institutional controls. Information on the uses and
limitations of these technologies is presented in EPA's
Handbook for Remedial Action at Waste Disposal Sites (U.S.
EPA, 1985a).
The final step in the alternative development process is to
develop a limited number of alternatives. In general, the
approach for developing alternatives applies to Class I and
Class II ground water. Class III ground water is treated
separately and is described in Section 5.4.2.
5.4.1 Ground Water That is a Current or
Potential Source of Drinking Water
A rapid remedial alternative generally should be developed for
ground water that is a current or potential source of drinking
water. This alternative should achieve the selected cleanup
level throughout the area of attainment within the shortest time
technically feasible. Additional alternatives should be
developed to ensure that a wide range of distinctive hazardous
waste management strategies are evaluated at most sites.
Natural attenuation to health-based levels often is a baseline
alternative for comparison with other alternatives.
Typically, three to five alternatives will be carried through to
detailed analysis. Screening criteria that can be used to
evaluate and narrow the range of alternatives are as follows:
! Effectiveness in reducing contaminant levels in the
plume, attaining AFxARs or other health-based levels,
and protecting human health and the environment
i
Implementability with respect to technical and
administrative feasibility of the alternatives and the
availability of needed technologies and services
A general cosf analysis to identify alternatives that are
significantly more costly than other alternatives that
achieve the same level of plume reduction
For ground water, a screening step is often unnecessary
because active restoration, containment, and natural
attenuation alternatives normally will be evaluated.
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General Response
Action
Active
Restoration
j
jt ,i -eni j
i
Attenuation
Components of
R&m&dtal Action
Tmasment Options
Discharge
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i ig
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Technology
n etcep-or ra its
Chemical
OffSiSe Treatment
, erinal
- '
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Deep Well injedion
Slurry Walts, Other
Vertical Barfiere
Low Peimeabihiy
Caps and Liners
._*».
Sere of we'ls to exl-aet -ontarninj'ed around water
in-jscljon wfi-Hs onsfte tt? in|&ct tincontamsnated or tf&ated
water to increase flow raSe to sx'ractsori we^Hs
pefmeabfe rned^a to mtercept and called contaminated ground
water
Biofo^'CS- !T,0c('fsCi3sion or dgstriBcti-on
Chernicalmo*,c*0nQrdeS,u«,on
Treatment at PQTW or RQRA facility
Rh s^ea1 separat-on o* rcmrentr^oo
"H^ermsl desfaic^on of waste
to ires* m plats
Oischnrg^ treated or untreated ground wale* icsonste surface
ReiPiect iteaffcd ground wale*1 So aquiies
Discharge treated cr untreated gr&und waiar to regulatKf deep
vvs!? !Ti£&ct)on system
Dfschssrge Sealed or untreated ground watef to local POTW
Discharge treated grourvd water so water supply system
IrtstitaNn^al control way include de^d ?esirsc§tong,
t ±< »
Use of ftydrau'Uc gradient tt> cO'dtrot tlow
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a e& o o«.n\0 ^a !ecson
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acf^ui&itson o^ ground water rights and we-i& fo snonitos
Flgyra S-3 General R0sponse Actions and Process Options for Ground Water.
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Alternatives that do not meet ARARs or protect human health
and the environment should be screened out, as should
alternatives that are orders of magnitude more costly than
other protective alternatives, or that pose implementability
problems that are high relative to other protective alternatives,
as reflected by the cost and time needed to surmount the
problem.
5.4.2 Ground Water That Is Not Current or
Potential Drinking Water
If a Superfund site has ground water that is unsuitable for
human consumption i.e., Class III, a limited number of
alternatives should be developed on the basis of the specific
site conditions. Environmental receptors that are potentially
affected or other beneficial uses such as agricultural or
industrial uses, will often be the critical factors used when
selecting cleanup levels. Also, the spread of contamination to
uncontaminated drinkable ground water should be prevented,
as should further migration from the source. If Class III ground
water is interconnected with ground water that is a current or
potential drinking water source, i.e., Class I or Class II,
remediation may be required to protect the higher use ground
water. The range of ground-water remedial alternatives
developed for Class III ground water will usually be relatively
limited, and the evaluation will be less extensive than for
Class I or Class II ground water.
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Chapter 6
Detailed Analysis of Alternatives and Selection of Remedy
6.1 Introduction
During the detailed analysis, remedial alternatives that have
been retained from the alternative development phase are
analyzed against nine evaluation criteria, which are described
in this chapter. The purpose of the detailed analysis is to
compare alternatives so that the remedy that offers the most
favorable balance among the nine criteria can be selected.
This chapter discusses these evaluation criteria and how they
may apply to sites with ground-water contamination.
An example of how the criteria are used at a
particular site is presented in the case study, found in
Appendix A.
6.2 Evaluation Criteria
The analysis of a remedial action for ground water is made on
the basis of the following nine evaluation criteria:
! Overall protection of human health and the
environment
! Compliance with ARARs
! Long-term effectiveness and permanence
! Reduction of toxicity, mobility, or volume
! Short-term effectiveness
! Implementability
! Cost
! State acceptance
! Community acceptance
The first two criteria are actually requirements; the selected
remedy must protect human health and the environment and
attain ARARs or provide grounds for invoking a waiver.
Alternatives are analyzed using the next five criteria to
determine how they compare to one another and to identify
tradeoffs between them. The final two criteria are modifying
considerations and can only be evaluated in the FS to the
extent that the affected state and community have submitted
formal comments at this point in the process. Typically, these
considerations will not be taken into account until the ROD is
prepared following the public comment period on the proposed
plan and RI/FS report.
Chapter 7 of the RI/FS Guidance (U.S. EPA, 1988c) presents
a recommended format for conducting the detailed analysis.
The basic features of each of the alternatives are described.
Then, a comparative analysis is undertaken to examine the
relative performance of the alternatives under each of the nine
criteria. A narrative discussion and summary table are
prepared for each part of the detailed analysis. The
recommended remedy must be protective, attain ARARs, be
cost-effective, and use permanent solutions and treatment
technologies to the maximum extent practicable, which is
determined primarily by balancing the next five criteria, as
modified by state and community acceptance.
6.2.1 Overall Protection of Human Health and the
Environment
This criteria addresses whether the remedy is protective of
human health and the environment considering the site's
characteristics. The remedy's long-term effectiveness and
permanence, short-term effectiveness, toxicity, mobility, and
volume reduction affect the evaluation of this criterion. How
each alternative achieves protection over time and whether
site risks are eliminated, reduced, or controlled are also
analyzed.
At sites with ground-water contamination, overall protection
from ground-water contaminant exposure is based largely on
the certainty that a remedy can achieve and maintain cleanup
levels.
6.2.2 Compliance with ARARs
Unless a waiver has been obtained for a particular ARAR or an
ACL under Section 121(d)(2)(B)(ii) has been obtained for a
chemical-specific ARAR, the selected remedy must comply
with all location-, action-, and chemical-specific ARARs.
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Six waivers to meeting ARARs are contained in CERCLA.
They include the following:
! Interim remedy
! Greater risk to human health and the environment
! Technical impracticability
! Equivalent standard of performance
! Inconsistent application of State requirements
! Fund-balancing
These waivers and their potential use at sites with ground-
water contamination are explained below.
6.2.2.1 Interim Remedy
An interim remedy can be part of the final remedy or it can be
a partial remedy that is implemented while the final remedy is
under construction or while the necessary arrangements for
the final remedy (e.g., obtaining permits) are made. This
waiver generally would not be used for ground-water
contamination situations unless the ARAR for an operable unit
that was taken as a final action was being waived. For
example, long-term storage of treatment residuals while a
process for managing the residuals is being arranged may
require a waiver of applicable land disposal restrictions.
6.2.2.2 Greater Risk to Human Health and the
Environment
If meeting an ARAR requires a remedial action that could
increase health or environmental risk, and that remedial action
was considered solely to meet an ARAR, the ARAR should
be waived. Also, the effect on public and worker safety of
implementing such a remedy should be assessed. For
example, if State air standards require that a carbon
adsorption unit be placed on an air-stripper designed to
remove volatiles from contaminated ground water, but naturally
occurring radionuclides in the ground water accumulate on the
carbon to the extent that risk levels increase, it may be
appropriate to waive the ARAR.
Factors that should be considered when invoking this waiver
include the magnitude, duration, and reversibility of the
adverse effects. In addition, the implications of meeting or not
meeting an ARAR must be weighed before the waiver can be
justified.
6.2.2.3 Technical Impracticability
Technical impracticability implies an unfavorable balance of
engineering feasibility and reliability. The term "engineering
perspective" used in CERCLA implies that cost, although a
factor, is not generally a major factor in the determination of
technical impracticability. This waiver may be used when
neither existing nor innovative technologies can
reliably attain the ARAR in question; or attainment of the
ARAR is not practicable from an engineering perspective. For
ground-water remedies, technical impracticability may be
measured in terms of restoration time frame. A time frame
beyond 100 years would generally warrant the technical
impracticability waiver.
6.2.2.4 Equivalent Standard of Performance
This waiver is used when an ARAR is stipulated by a
particular design or operating standard, but equivalent or
better results (e.g., contaminant levels, worker safety, or
reliability) could be achieved using an alternative design or
method of operation.
It is anticipated that this waiver will generally be inappropriate
for ground-water remedies, as most ARARs for ground-water
are chemical specific rather than action specific.
6.2.2.5 Inconsistent Application of State
Requirements
This waiver is intended to prevent unreasonable restrictions
from being imposed on remedial actions. A standard must be
promulgated in order for it to be an ARAR. This waiver is used
in two situations: (1) when State requirements have been
developed and promulgated but never applied because of their
lack of applicability in past situations (such requirements
should not be applied in CERCLA actions if there is evidence
that the state does not intend to apply them to non-CERCLA
actions that are otherwise similar); and (2) when State
standards have been variably applied or inconsistently
enforced.
The consistency of application may be determined by:
! Similarity of sites or response circumstances (nature of
contaminants or media affected, characteristics of waste
and facility, degree of danger or risk, etc.)
! Proportion of non-compliance cases (including
enforcement actions)
! Reason for non-compliance
! Intention to consistently apply future requirements as
demonstrated by policy statements, legislative history,
site remedial planning documents, or State responses to
sites at which EPA is the lead agency. Newly
promulgated requirements are presumed to embody this
intention unless there is contrary evidence.
6.2.2.6 Fund-Balancing
The Fund-balancing waiver may be invoked when meeting an
ARAR would entail extremely high costs in relation to the
added degree of protection or reduction of risk afforded by that
standard and when remedial action at other sites would be
jeopardized
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(because of lack of funds) as a result. The following criteria
should be considered when invoking the Fund-balancing
waiver for ARARs:
! Cosf-Fund balancing is only appropriate if the relative
level of the cost is high.
! Availability of Superfund Monies to Respond to Other
S/tes-Projections should show that significant threats
from other sites may not be addressed under the current
level of Superfund monies.
6.2.3 Long-Term Effectiveness and
Permanence
The next criterion used to evaluate and compare alternatives
is long-term effectiveness and permanence. This criterion
addresses how well a remedy maintains protection of human
health and the environment after remedial action objectives
have been met. Components of analyzing long-term
effectiveness include examining the magnitude of residual risk
and the adequacy and long-term reliability of management
controls. For example, a ground-water remedy involving
recharge might be selected because recharge preserves the
ground water as a resource while the remedy is in place as
well as after the action is terminated. The source control
action will also affect the long-term effectiveness of the
ground-water remedy since actions that do not fully address
migration from the source or that have a lower probability of
reducing or eliminating contaminant migration to ground water
will ultimately reduce the effectiveness of the ground water
action. The probability of attaining cleanup levels, particularly
in complex or technically limiting situations such as those
described in Section 5.3.3.2, should also be considered under
this criterion.
6.2.4 Reduction of Mobility, Toxicity, or Volume
The anticipated performance of treatment technologies used
in the alternatives is evaluated under this criterion. The
amount of hazardous material destroyed or treated and the
amount remaining onsite is assessed, along with the degree
of expected reduction in mobility, toxicity, or volume. In
addition, the degree to which the treatment is reversible is
evaluated. For ground water, this might be evaluated by
calculating the proportion of the contaminant plume that is
remediated. This criterion is also related to the preference for
treatment as a principal element. In determining whether the
preference is satisfied, all of the principal threats posed by the
site must be considered. Ground-water contamination will
typically comprise a principal threat at many Superfund sites,
but if source or soil threats are also present, treatment only of
ground water would not satisfy the preference.
6.2.5 Short-Term Effectiveness
The effectiveness of the alternative in protecting human health
and the environment during construction and implementation
is assessed under the short-term effectiveness criterion. The
length of time required to achieve protection, the short-term
reliability of the technology, and protection of the community
and of workers during remediation are considered. The time
frame for plume removal is analyzed with reference to onsite
and offsite human and environmental exposure points. This
evaluation should include consideration of short-term and
cross-media impacts that may be posed during
implementation of the remedy. Short-term effects such as the
disruption to residential neighborhoods or sensitive
environments caused by construction of a slurry wall, for
example, should also be evaluated.
6.2.6 Implementability
The technical and administrative feasibility of alternatives as
well as the availability of needed goods and services are
evaluated to assess the remedy's implementability. The
factors that make up the implementability criterion are as
follows:
! Ability to construct, operate and maintain the
technology; e.g., a slurry wall generally is more difficult
to construct than a ground-water extraction system
alone and thus may receive a less favorable evaluation
under this criterion.
! Ability to phase in other actions, if necessary; e.g., a
ground-water extraction system implemented prior to the
source control action may restrict the type of source
control actions that could be implemented.
! Ease of undertaking additional remedial actions, if
necessary; e.g., the capacity of an air-stripper and its
ability to treat larger volumes of ground water may make
it a more favorable option than an alternative using a
system limited to low ground-water flow rates.
! Ability to monitor the effectiveness of the remedy; e.g.,
variations in ground-water monitoring requirements, the
length of time that monitoring is required, the frequency
of monitoring, and the depth of monitoring might be
compared for different alternatives.
! Ability to obtain approvals and permits from other
agencies (for offsite actions); e.g., obtaining approval to
discharge to a POTW may be more difficult than meeting
the substantive NPDES requirements for discharging to
surface water.
! Coordination with other agencies; e.g., certain remedies
may require more coordination with local agencies, such
as approval to discharge to a POTW.
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! Availability of hazardous waste treatment, storage, and
disposal facilities to dispose of treatment residuals, and
their capacity; e.g., remedies that generate ground-water
treatment residuals such as sludges or spent carbon
may be less favorable under this criterion than remedies
that do not.
! Availability of necessary equipment and specialists; e.g.,
innovative treatment techniques may be less
implementable than treatment techniques that are in
common use.
6.2.7 Cost
Capital and operation and maintenance costs are evaluated for
each alternative. These costs include design and construction
costs, remedial action operating costs, other capital and
short-term costs, costs associated with maintenance, and
costs of performance evaluations, including monitoring. All
costs are calculated on a present worth basis.
6.2.8 State Acceptance
This analysis will usually be deferred to the ROD following
receipt of public comments. During the FS, it is limited to
formal comments made by the state during previous phases
of the RI/FS. Technical and administrative issues that the
state may have concerning each alternative action are
identified and analyzed. Features that the state supports,
features that the state may have reservations about, and
features that the state opposes are discussed.
6.2.9 Community Acceptance
The evaluation of community acceptance is analogous to the
evaluation made for State acceptance and generally is
deferred until ROD preparation. Comments received from the
public are assessed to determine aspects of each remedy
that are supported or opposed.
6.3 Selection of Remedy
The selection of a remedial action from among alternatives is
a two-step process. First, a preferred alternative is identified
and presented to the public in a proposed plan along with the
supporting information and analysis for review and comment.
Second, the lead agency reviews the public comments,
consults with the support agency to evaluate whether the
preferred alternative is still the most appropriate remedial
action for the site, and makes a decision.
As discussed in Section 6.1, the remedies are selected by
balancing the nine evaluation criteria. First, it should be
confirmed that all alternatives provide adequate protection of
human health and the environment and either attain or exceed
all of their ARARs or provide grounds for invoking a waiver of
an ARAR. As part of the balancing, total costs of each
alternative should be compared to the overall
effectiveness each affords. The costs and the overall
effectiveness of the alternatives should be examined to
determine which alternatives offer results proportional to their
costs. This might be accomplished by comparing the relative
plume reduction to the cost for various restoration alternatives.
The preferred alternative is selected by evaluating the relative
long-term effectiveness; short-term effectiveness; reduction in
toxicity, mobility, or volume; implementability; and cost of the
alternatives. The alternative that represents the best
combination of those factors deemed most important to the
site will be chosen. In performing the necessary balancing,
the preference for remedies involving treatment as a principal
element must be considered. The proposed plan will identify
the alternative that appears to offer the best balance of the
tradeoffs among the alternatives in terms of the criteria and
confirm the expectation that all statutory requirements would
be satisfied.
In making the final selection, the balancing is reassessed in
light of any new information or point of view expressed in the
comments. The relationship between costs and overall
effectiveness is reexamined and the balancing analysis is
reevaluated, this time taking into account not only the
preference for treatment as a principal element, but also the
modifying considerations of State and community
acceptance. After this step, either the original preferred
alternative or another cost-effective alternative that provides a
better combination of the balancing criteria is selected. Using
this process, the selected remedy will represent the
protective, cost-effective solution for the site or problem that
uses permanent solutions and alternative treatment (or
resource recovery) technologies to the maximum extent
practicable. This finding, along with a discussion of how each
of the statutory requirements are satisfied, should appear in
the ROD.
Typically, a ROD for ground-water action should include the
following components:
! A summary of the site characterization and baseline
risk assessment performed in the Rl
! A summary of the alternatives examined in detail and
the comparative analysis undertaken in the FS
! Remedial action objectives defined in the FS; for the
selected remedy, the ROD should describe:
- Cleanup levels
- Area of attainment
- Estimated restoration time frame
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! A description of technical aspects of the remedy, such
as the following:
Expected pumping and/or flow rates
Number of extraction wells
Treatment process
Control of cross-media impacts
Management of residuals
Gradient control system description
Type of institutional controls and implementing
authority
In many cases, the performance of remedies for restoring
contaminated ground water can only be evaluated after the
remedy has been implemented and monitored for a period of
time. The remedial action objectives should be presented as
estimates or ranges so that a reasonable degree of change
can be
accommodated during the design and implementation without
having to develop a new ROD. A variation of this is to allow for
a reasonable degree of change in the goal of the remedy
based on experience gained during remediation. For example,
a ground-water extraction and treatment remedy might include
two scenarios: (1) ground-water extraction continues until
cleanup goals are attained or (2) ground-water extraction
continues until contaminant levels in the extracted water
reach a constant value or asymptote (e.g., contaminant mass
is no longer being removed at significant levels), at which point
portions of the plume that remain above the cleanup levels are
managed through containment and use of institutional
controls. This type of remedy has been used in the
underground storage tank program.
The information that should be presented in the ROD for an
interim action operable unit can be found in Appendix C.
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Chapter 7
Evaluating Performance and Modifying Remedial Actions
7.1 Introduction
Even when a detailed hydrogeologic investigation has been
performed, the complex behavior of contaminants in ground
water, combined with the heterogeneity of hydrogeologic systems,
make predicting the effectiveness of remediation difficult. This
chapter presents a conceptual discussion of evaluating
performance and modifying remedial actions. Administrative
requirements associated with changes in a remedial action and
elements of a performance evaluation program are identified and
discussed.
Performance evaluations of the full-scale remedial action, based
on the monitoring data discussed in Section 7.4, are conducted
periodically to compare actual performance to expected
performance. The frequency of performance evaluations should
be determined by site-specific conditions. Conducting
performance evaluations and modifying remedial actions is part
of a flexible approach to attaining remedial action objectives.
Decisions can be verified or modified during remediation to
improve a remedy's performance and ensure protection of human
health and the environment.
7.2 Modifying Decisions
Figure 7-1 represents a decrease in contaminant concentration
over time for three ground-water remedial actions of varying
effectiveness. Line A represents a remedial action that is meeting
design expectations, and the desired cleanup levels are predicted
to be reached within the anticipated time. Line B represents a
remedial action that is predicted to achieve the cleanup levels, but
the action will have to be operated longer than anticipated. Line
C represents a remedial action that will not achieve the desired
cleanup levels for a long time, if ever, without modifying the
remedial action. Performance evaluations provide information
about whether remedial action objectives can be met using the
selected alternative.
Performance evaluations should be conducted 1 to 2 years after
startup to fine-tune the process. More extensive performance
evaluations should be
conducted at least every 5 years. After evaluating whether cleanup
levels have been, or will be, achieved in the desired time frame,
the following options should be considered:
! Discontinue operation
! Upgrade or replace the remedial action to achieve the
original remedial action objectives or modified remedial
action objectives
! Modify the remedial action objectives and continue
remediation, if appropriate
The performance evaluation program may indicate that the
remedial action objectives have been met and the remedy is
complete. In other cases, operational results (e.g., contaminant
mass removal has reached insignificant levels) will demonstrate
that it is technically impracticable to achieve cleanup levels in a
reasonable time, and a waiver to meeting ARARs may be
required. Additional information, onsite conditions, or other factors
may indicate that clean up levels can be adjusted to less stringent
levels and still protect human health and the environment.
These options provide the decision-maker with flexibility to
respond to new information and changing conditions during the
remedial action. Figure 7-2 illustrates this flexible decision
process.
7.3 Modifications to Records of Decision
Three types of changes can occur in a remedy following ROD
signature: minorchanges, significant changes, and fundamental
changes. Minor changes, such as the decision to move the
location of a well or minor cost or time changes, are those
technical or engineering changes that do not significantly affect
the overall scope, performance, or cost of the alternative and fall
within the normal scope of changes occurring during the remedial
design/remedial action engineering process. Such changes
should simply be documented in the post-decision documentfile
and, optionally, can be mentioned in a remedial design fact sheet,
which is often issued as part of the community relations effort.
Significant changes to the remedy in terms of scope,
performance, or cost are explained in an Explanation
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Contaminant
Concentration
Actual Performance
Predicted Performance
C. Will Not Attain Cleanup Level
and Restoration Time Frame
B, Cleanup Level Will Be Attained,
but Restoration Time Frame
Will be Long
A. Will Achieve Original Cleanup
Level and Restoration Time Frame Goals
Cleanup Level
Restoration Time Frame
Time
Remedial Action Objectives
i -Time at which ground-water treatment system Is evaluated
to assess its effectiveness at meeting the original
response objectives.
Figure 7-1 Predicting Remedial Action Performance from Monitoring Data.
of Significant Differences provided for under CERCLA Section
117(c). This document describes the differences and what
prompted them and is announced in a newspaper notice. This
is placed in the administrative record for the site, along with
the
information that prompted the change. Significant changes
involve a component of the remedy, such as a change in the
volume of contaminated ground water that must be addressed,
or a switch from air stripping to carbon adsorption in a ground-
water pump and
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Remedy
Complete.
Implement Remedy/
Monitor Performance
Have
Remedial
Action
Objectives
een Me
Remedy/
Meeting Design
Expectations
Conduct Performance Evaluation
Revise
Remedial
Action
Objective
Upgrade/Replace
Remedy
Establish Revised Remedial
. Action Objectives
Upgrade, Replace,
or Maintain Remedy
Continue Operation/Monitoring
Figure 7-2 Flexible Decision Process for Ground-Water Remedial Actions.
treat remedy, but do not fundamentally alter the hazardous
waste management strategy represented by the selected
remedy.
Fundamental changes are changes in the overall waste
management strategy for the site; they require amendments
to the original ROD. A change from active restoration to
passive restoration would be considered a fundamental
change. Procedures for
amending a ROD are the same as for issuing a ROD. They
include the following:
! Preparation of a proposed amendment
! Issuance of a newspaper notice announcing the
proposed amendment
! A public comment period
! Finalization of the amendment
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! Preparation of a responsiveness summary
! Placement of the amendment and responsiveness
summary into the administrative record
! Publication of a newspaper notice announcing
finalization of the amendment
7.4 Performance Monitoring
This section provides guidelines for using ground-water
monitoring data to evaluate performance. It does not provide
detailed information on technical aspects of ground-water
monitoring, such as well installation techniques or sampling
procedures. The TEGD (U.S. EPA, 1986e) is one resource for
this information.
The monitoring system should be designed to provide
information that can be used to evaluate the effectiveness of
the remedial action with respect to the following:
! Horizontal and vertical extent of the plume and
contaminant concentration gradients, including a mass
balance calculation, if possible
! Rate and direction of contaminant migration
! Changes in contaminant concentrations or distribution
over time
! Effects of any modifications to the original remedial
action
! Other environmental effects of remedial action, such as
saltwater intrusion, land subsidence, and effects on
wetlands or other sensitive habitats
7.4.1 Well Locations
Because ground-water contamination problems are site
specific, the number and locations of monitoring wells must
suit site conditions and the remedial action selected. In
general, wells should be located upgradient (to detect
contamination from other sources), within the plume (to tract
the response of plume movement to the remedial action), and
downgradient (either to verify anticipated responses or to
detect unanticipated plume movement). Also, monitoring
should reflect both horizontal and vertical ground-water flow.
If a containment system is used, wells or other detection
devices should also be located where contaminant releases
are most likely to occur.
7.4.2 Sampling Duration and Frequency
A determination that the remedial action is complete may
require a statistical analysis of contaminant levels. The Office
of Policy, Planning, and Evaluation
is preparing guidance for using statistics to assess ground-
water monitoring data. Also, OSW has prepared guidance for
using statistics to evaluate ground-water monitoring data at
RCRA sites (U.S. EPA, 1987m). This guidance may provide
useful information for Superfund sites as well.
The intervals between sampling events should be shortest at
the beginning of the remedial action. In many cases, monthly
sampling intervals may be reasonable during the first year.
Data collected during the first year may be used to assess
gaps in the data, further characterize the aquifer, identify
locations for additional monitoring, and evaluate sources of
uncertainty, such as sampling, analysis, and site conditions.
The recommended long-term frequency for sampling depends
in part on the effectiveness of the remedial action as
determined through the ongoing monitoring program. If
monitoring shows a steady, predictable decrease in
contaminant concentrations in the aquifer, reducing the
sampling frequency may be reasonable. The determination of
long-term sampling frequency may also depend on the rate of
plume migration, the proximity of downgradient receptors, and
the variability of the ground-water data and the degree of
confidence needed for achieving the cleanup level at a specific
location. Quarterly sampling may be reasonable for long-term
monitoring at some sites.
Monitoring data provide the basis for determining when
remedial action objectives have been met and when the
remedial action is complete. Special analytical services may
be needed in some cases to confirm cleanup levels that are
lower than the standard detection limit. Operation should
continue for a limited time after cleanup levels have been
achieved. In many instances, contaminant levels in the aquifer
increase when pumping is terminated because contaminants
are allowed to re-equilibrate in the ground water. This
phenomenon would be observed if the rate at which ground
water was removed through pumping is greater than the rate
of desorption of contaminants. Monitoring programs should
therefore ensure that ground water is sampled until any
residual contaminants could have desorbed from the aquifer
material.
7.4.3 Source Control Monitoring
Another goal of performance monitoring is to ensure that any
source control action completed at the site effectively prevents
further degradation of ground water. To achieve this goal, it
may be necessary to monitor the unsaturated zone using
techniques such as soil-gas monitoring to detect
contaminants before they reach the ground water.
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References
Barnhouse, L. W., et al., "Users Manual for Ecological Risk
Assessment," Environmental Services Division,
Publication No. 2679, Oak Ridge National Laboratories,
Oak Ridge, Tennessee, 1986.
Bell & Howard Company, Groundwater and Wells, 1980.
52 Federal Register 12876, April 7,1987; 50 Federal
Register 49636-497022, November 13, 1985; 52 Federal
Register 25690-25717, July 8, 1987.
Fetter, C. W., Jr., AppliedHydrogeology, Merrill Publ.
Co., 2nd Edition, 1988.
National Water Works Association and U.S. EPA, Methods
for Determining the Locations of Abandoned Wells,
1987.
Robert S. Kerr Environmental Research Laboratory,
"Applications and Limitations of Leaching Tests: Soil
Residuals Effect on Water Quality," April 6, 1988a.
Robert S. Kerr Environmental Research Laboratory,
"Applications and Limitations of Leaching Tests:
Facilitated Transport," April 13, 1988b.
Robert S. Kerr Environmental Research Laboratory,
"Applications and Limitations of Leaching Tests: Flow
and Transport in Treated Media-Models for Decision
Makers," April 12, 1988c.
Robert S. Kerr Environmental Research Laboratory,
"Applications and Limitations of Leaching Tests:
Groundwater Sampling for Metal Analyses," April 8,
1988d.
U.S. Department of Energy, "Ground Water Workstation
Implementation and Configuration Management Plans,"
Oak Ridge National Laboratory, October 15, 1986.
U.S. Department of Energy, "Ground Water Workstation
User's Manual," Oak Ridge National Laboratory, April
26, 1988.
U.S. EPA, "Additional Interim Guidance for FY '87 Records
of Decision," OSWER Directive 9355.0-21, July 24,
1987a.
U.S. EPA, Alternate Concentration Limit Guidance,
OSWER Directive 9481.00-6C, EPA/530-SW-87-017,
July 1987b.
U.S. EPA, The CERCLA Compliance with Other Laws
Manual, draft, August 1988a.
U.S. EPA, Compendium of Superfund Field Operations
Methods, EPA/540/P-87/001a and b, 1987c.
U.S. EPA, Data Quality Objectives for Remedial
Response Activities, EPA 540/G-87/003a, 1987d.
U.S. EPA, "Draft Guidance on Preparing Superfund
Decision Documents: The Proposed Plan and Record of
Decision," OERR, March 1988b.
U.S. EPA, "Geophysics Advisory-Expert System,"
Environmental Monitoring and System Laboratory,
EPA/660/X-88/257, 1988g.
U.S. EPA, Ground-Water Protection Strategy, Office of
Ground-Water Protection, August 1984.
U.S. EPA, Guidance for Applicants for State Wellhead
Protection Program Assistance Funds Under the Safe
Drinking Water Act, Office of Ground-Water Protection,
June 1987e.
U.S. EPA, Guidance for Conducting Remedial
Investigations and Feasibility Studies Under CERCLA,
Interim Final, 1988.
U.S. EPA, Guidance Document for Providing Alternate
Water Supplies, OSWER Directive 9355.3-01, October,
1987f.
U.S. EPA, Guidelines for Delineating Wellhead Protection
Areas, Office of Ground-Water Protection,
EPA/440/6-87-010, June, 1987g.
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U.S. EPA, "Guidance for Health Risk Assessment of
Chemical Mixtures," 51 Federal Register 34014,
September 24, 1986a.
U.S. EPA, "Guidance on Preparing Superfund
Decision Documents," March, 1988f.
U.S. EPA, Guidelines for Ground-Water Classification
Under the EPA Ground-Water Protection Strategy,
Office of Ground-Water Protection, draft, December
1986b.
U.S. EPA, Handbook for Remedial Action at Waste
Disposal Sites, October 1985a.
U.S. EPA, Health Advisories for Legionella and Seven
Inorganics, March 1987, NTIS No. PB87-235586;
Health Advisories for 25 Organics, March 1987, NTIS
No. PB87-235578; Health Advisories for 16 Pesticides,
March 1987h; PB87-200176.
U.S. EPA, Integrated Risk Information System, Volumes I
and II, EPA/600/8-86/032 a and b, 19871.
U.S. EPA, "Interim Final Guidance on Removal Action
Levels at Contaminated Drinking Water Sites," OSWER
Directive 9360.1-01, October 6, 1987J.
U.S. EPA, "Interim Guidance on Compliance with
Applicable or Relevant and Appropriate Requirements,"
OSWER Directive 9234.0-05, July 9, 1987k.
U.S. EPA, "Interim Guidance on Funding for Ground and
Surface Water Restoration," OSWER Directive
9355.023, October 26, 19871.
U.S. EPA, "Interim Guidance on Superfund Selection of
Remedy," OSWER Directive 9355.0-19, December 24,
1986c.
U.S. EPA, Modeling Remedial Actions at Waste Disposal
Sites, EPA/540/2-85-001, April, 1985b.
U.S. EPA, National Contingency Plan, 40 CFR Part
300, 1985.
U.S. EPA National Contingency Plan, 40 CFR Part
300-Proposed December 21, 1988 Federal Register,
1988d.
U.S. EPA, Quality Criteria for Water, 1986, EPA
440/5-86-001, 1986d.
U.S. EPA, "Removal Program Priorities," OSWER
Directive No. 9360.0-18, March 31, 1988e.
U.S. EPA, RCRA Ground-Water Monitoring
Technical Enforcement Guidance Document (TEGD),
OSWER Directive 9950.1, 1986c.
U.S. EPA, "Statistical Analysis of Ground Water at
RCRA Sites," Draft Final, October 20, 1987m.
U.S. EPA, Superfund Exposure Assessment Manual,
EPA/540/1-88/001, April 1988.
U.S. EPA, Superfund Public Health Evaluation
Manual, EPA/540/1-86/060, October 1986f.
U.S. EPA, Superfund Removal Procedures, OSWER
Directive No. 9360.0-03B, February 1988f.
U.S. EPA, Water Quality Standards Handbook, December
1983.
van der Leeden, F., ed., Geraghty and Miller's Groundwater
Bibliography, Water Information Center, 1987.
Verschueren, K. Handbook of Environmental Data on
Organic Chemicals, Second Edition, Van Nostrand
Reinhold Company, New York, 1983.
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Appendix A
Case Study with Site Variations
A-1 Site Location and Background
The Hypo-Thetical site, located on 50 acres near a suburban
area in the Midwest, is an industrial landfill that received heavy
commercial use. On the basis of interviews and the site
history, it is believed that the hazardous wastes disposed at
the site were organic solvents from a solvent recycling firm
that has since ceased operation. Apparently, the firm also
used a small area of the site to clean auto interiors with
organic solvents.
Currently, nearby residents use wells for drinking water; 50
active wells have been identified in the area. The ground water
is not an irreplacable source of drinking water because
domestic water use could economically be tied into a
municipal water supply system that relies on surface water
reservoirs from a nearby mountain range. For this reason, the
ground water used for drinking water is classified Class IIA for
the purpose of the Superfund remedial activities.
A.2 Ground-Water Considerations
During Scoping
During scoping, several questions were raised to assist in
planning the RI/FS. These are identified and discussed in the
following paragraphs.
What Is the Existing Information?
The following important information, related to exposure
pathways, the hydrogeology of the site, and contaminants
disposed at the site, was known during the scoping phase:
! Nearby residents are potentially exposed through the
drinking water ingestion pathway. Heavy population
growth is anticipated in the area; developers (HazVelop,
Inc.) have already approached the county regarding
residential development of the site in 5-acre parcels, in
which homeowners would use private wells and septic
fields.
! Potential exposure pathways to workers at commercial
facilities near the site have not been identified.
! On the basis of existing drinking water well logs, shallow
and deep ground water have been identified. The deep
ground water, lying approximately 130 feet below the
surface, is used for drinking water and is classified Class
IIA. From a purview of the available well logs and a study
of county and State hydrogeologic publications, the deep
ground water appears to flow to the southeast. The
shallow ground water, which has not yet been classified,
was assumed to flow to the southeast as well, since the
topography of the site slopes in this direction.
The shallow zone, which appears to be perched on a
clay layer, was noted at about 20 feet below the surface
in some wells logs. In addition, well construction details
indicate that gravel packs in some of the domestic wells
extend from the shallow to the deep zones, thus
providing a conduit for vertical movement of contaminants
from the shallow zone.
The site is located on glacial outwash.
During the site inspection, an inlet to an under-ground
storage tank was found. The tank was probably used to
store solvents.
Soil analyses conducted during the site inspection
indicate that contaminants are probably limited to VOCs.
At the conclusion of the site inspection, it was not clear
if there were hot spots at the site that could be defined.
Is a Removal Action Warranted at the Site?
Domestic well samples taken during the site inspection
indicated no contaminants above removal action levels; and a
removal action did not appear justified based on the available
site information. A fence was constructed to restrict public
access to the facility.
What Are the Potential Exposure Scenarios?
To evaluate potential exposure scenarios, several
ground-water monitoring wells were installed and screened in
the shallow saturated zone. They were located in an area that
is expected to be downgradient of the source. Contaminants
were detected at the maximum concentrations shown in Table
A-1. Aside from those expected to have originated from the
site, no contaminants were
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Table A-1. Concentrations of Chemicals In Ground Water
Hypo-Thetical Site
Chemical
Range of
Concentrations
Reported3 ( g/l)
Volatile Organic Compounds
Benzene
Bromadichloromethane
Carbon disulfide
Chloroethane
1,1-Dichloroethene
Trans-1,2-dichloroethene
Methylene chloride
Phenol
Tetrachloroethene
1,1,1 -Trichloroethane
Trichloroethene
Vinyl chloride
Phthalates
Bis(2-ethylhexyl)phthalate
Di-n-butyl phthalate
20-120
5-56
10-67
15-1,000
50 - 1,900
37 - 1,000
10-80
20 - 1,500
45 - 650
12-1,500
6-1,200
45 - 500
10-90
8-45
Inorganics
Aluminum
Barium
Calcium
Copper
Iron
Lead
Magnesium
Manganese
Nickel
Potassium
Sodium
Zinc
440
99
10,300
20
999
5
4,000
70
2
1,500
6,550
32
-600
-200
- 20,750
-80
- 1 ,500
-7
- 7,000
-80
-5
- 2,000
-10,000
-50
Excludes samples in which the contaminant was not
detected.
detected above health-based levels in the shallow ground
water; therefore, it has been classified Class MB, a potential
source of drinking water. High contaminant levels near the
underground tank indicate that the tank leaked or that some
solvent was spilled when the tank was being filled.
The potential exposure scenarios that were identified during
scoping include the following:
! Direct contact with contaminated soil by trespassers,
including children who play at the site and teenagers
who use the site for dirt biking
! Inhalation of VOCs from the vadose zone by nearby
residents and workers (subsequent air sampling
performed onsite indicated that contaminants are not
present at detectable levels)
! Ingestion of contaminated ground water if the deep
ground water is or becomes contaminated or if the
shallow aquifer is used
What Are the Probable Ground-Water Response
Objectives?
For both deep and shallow ground water, the ground-water
response objectives are as follows:
Prevent exposure to any contaminated drinking water
Prevent contamination of the deep ground water, if it is
indeed uncontaminated
Restore contaminated ground water for future drinking
water use
What Data Should Be Collected?
Data collected during the Rl will be used to assess exposure
from ground water and to characterize contaminant behavior
in ground water as it affects remedy selection. Many of the
ground-water remedies appropriate for this site require
ground-water extraction. The data that should be collected to
assess exposure include domestic well samples and
monitoring well samples in both the deep and the shallow
ground water. The data-collection effort that will be undertaken
to characterize contaminant behavior as it affects remedy
selection and its estimated costs include:
! Monitoring wells and piezometers in the deep and
shallow ground water to determine the extent of
contamination and interconnection between the aquifers
at a cost of approximately $1,500 per well for the shallow
wells and $6,000 per well for the deep wells
! TOC and contaminant concentrations in saturated soil
cores to evaluate partitioning to the soil phase at a cost
of $3,000 per sample for the analyses of volatiles,
semi-volatiles, total metals, cyanide, and major cations
and anions
! Aquifer test data to determine aquifer response and
extraction effectiveness at a cost of approximately
$15,000
! Contaminant degradation information
A.3 Removal Action
During the Rl, after several private wells had been sampled
and soil and ground-water data had been analyzed, it was
determined that a removal action for ground water based on
action levels or site-specific considerations was not warranted
and that interim actions and a final action were appropriate.
A.4 Interim Action
As an interim action, the tank was drained and excavated and
the surrounding soil was excavated and stored in a tank on
the site. A vapor extraction
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system was installed in the excavated area, and the pit was
backfilled. Low rate pumping of ground water was also
initiated in this area. The low rate was used to ensure that
pumping in this area would not increase contaminant
migration from other source areas. After ensuring that the
substantive requirements of the local POTW would be met,
ground water was treated using an air stripper with a granular
activated carbon system for air releases and discharged to a
storm drain. As part of the Rl, a well survey of the area was
completed and an abandoned deep well screened in both the
shallow and deep ground water was identified downgradient of
the contaminant plume. A second interim action to seal the
abandoned well was implemented.
To take these interim measures, a ROD, containing the
information summarized in Table A-2, was prepared, and the
five statutory requirements, listed below, were addressed:
! The action protected human health and the environment
by reducing expansion of the plume, hence decreasing
the likelihood of exposure. Contaminated soil was stored
in a tank on the site; access was limited to workers.
! ARARs were not attained in the ground water, but final
action to reach ARARs will be facilitated by the actions.
Contaminated ground water was treated to specified
pretreatment levels before being discharged to the storm
drain. In addition, air monitoring of the aeration system
indicated that releases did not exceed the levels
specified by State regulations.
! The ground-water extraction system was relatively low in
cost since the pumping rate was low. Both actions were
cost-effective according to cost comparisons between (1)
immediate prevention of plume expansion and (2)
long-term remediation of a much larger plume that would
be initiated 2 to 3 years after completion of the RI/FS
and remedy design and construction.
! The extracted ground water was treated to required
levels and thus met the statutory preference for
treatment. The well seal also met the statutory
requirement for permanent solutions to the maximum
extent practicable.
! The interim action permanently and significantly reduced
the volume of hazardous waste by removing and treating
contaminants in soil and ground water.
While this interim action was being implemented, site
characterization work continued, and the boundaries of
contaminated soil and ground water were delineated. The
interim action also aided the site
investigation by providing aquifer parameters based on data
from the pumping well. In addition to providing the hydraulic
conductivity of the shallow aquifer, a nearby observation well
screened in the deeper saturated zone indicated minimal
interconnection between the upper and lower zones in this
area.
A.5 Summary of the Rl Report
Constituents found in the soil and the ground water include
1,1-dichloroethene (1,1-DCE), 1,1,1-trichloroethane (TCA),
trichloroethene (TCE), tetrachloroethene (PCE), benzene,
methylene chloride, vinyl chloride, and other volatile organic
compounds (VOCs), as well as phenol, bis(2-ethylhexyl)
phthalate (DEHP), and di-n-butylphthalate.
In the soil, identified hot spots represent approximately 4,000
cubic yards of contaminated soil (see Figure A-1). The
concentration of VOCs in these hot spots is approximately
10,000 to 100,000 ppb. The volume of soil that is
contaminated in addition to the 4,000 cubic yards is about 20
acre-feet (approximately 2 acres of soil contaminated to an
average depth of 10 feet).
A continuous clay layer lies beneath the site, separating the
shallow aquifer from the deep aquifer over several acres.
Boring logs indicate that its thickness ranges from 15 to 20
feet, beginning at a depth of 40 to 45 feet below the surface.
A silty sand layer with hydraulic conductivity of approximately
10"3 cm/sec occurs above and below the clay layer. The
unconfined shallow aquifer is perched above the clay layer.
Although the hydraulic conductivity of the clay is low (10
cm/sec), the presence of solvents can increase the
conductivity. Consequently, monitoring of the lower aquifer
continued throughout the investigation and implementation of
the remedy. The clay layer drops to the southeast;
consequently, the unconfined shallow ground water moves to
the southeast, flowing at an estimated rate of 150 feet/year,
as determined from the low-rate pumping test of the shallow
ground water. At this rate, the plume will reach the edge of the
clay layer and potentially contaminate the deep ground water
in approximately 13 years, assuming there is no contaminant
retardation because of sorption. The unconfined deep ground
water moves to the southeast within the silty sand formation.
The deep ground water is not currently contaminated, but the
shallow ground water is. There is a localized TCE plume with
concentration levels in the 10,000 ppb range. This plume is
believed to be related to the interior auto-cleaning activities at
the site. A larger second plume covers 20 acres of the site.
This plume contains a greater variety of the contaminants
listed in Table A-1 and is believed to result from poor
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Table A-2. Evaluation of the Operable Unit Taken as an Interim Action
Criterion
Tank Removal, Vapor Extraction System, and
Ground-Water Extraction
Sealing Abandoned Well
Protects Human Health and the
Environment
Meets ARARs
Is Effective Over the Short-term
Yes, reduces spread of contaminants to potential
exposure points.
Meets ARARs for ground-water discharge; does not
meet ARARs in the aquifer (i.e..health-based
cleanup levels).
Removal of tanks would prevent further source
migration, soil-gas and ground-water
extraction would reduce contaminant levels at the
site and limit further contaminant migration.
Action would also increase the short-term
effectiveness of the final remedy.
Yes, reduces spread of contaminants to potential
exposure points.
Yes, meets State well-sealing standards.
Sealing the well would eliminate the potential for
contaminant migration through this conduit in the
short term.
Is Effective Over the Long-Term
Reduces Toxicity, Mobility, or
Volume
Is implementable
Is Cost-Effective
Meets State's Acceptance
Meets Community's Acceptance
Promotes long-term effectiveness by reducing
contamination at the site.
Reduces volume by removing and treating high
concentration zone
Action can be implemented with minimal
disruption of the ongoing investigation.
Installation and monitoring of extraction systems
will probably aid in the implementation of the final
remedy.
Action is expected to significantly reduce cost of
final remedy at the site by reducing the volume of
contaminated material to be remediated and by
providing valuable design and operation
information.
Yes, state approved.
Yes, community strongly supports any action to
remediate the site as early as possible, preventing
contaminant migration.
Sealing the well would eliminate the potential for
contaminant migration through this conduit in the
long term.
Not applicable to the scope of the action
Requires coordination between the water district, the
municipal water suppliers, and the well owner. Details
for the well sealing were discussed and agreed to at a
meeting between the involved parties.
Action is considered to be of low cost compared to the
cost of remediation if the contaminants migrate to the
deeper zone.
Yes, state approved.
Yes, community strongly supports any action to
remediate the site as early as possible, preventing
contaminant migration.
Comments: In addition to meeting the necessary statutory mandates, there was sufficient information to determine that these actions would not
exacerbate the site problem and that the action would be consistent with the final remedy for the site, the goal of which is to reduce
contaminant concentrations in the plume to heath-based levels.
management practices at the solvent recycling facility. The
degradation characteristics of the contaminants vary; some of
the organics degrade under natural conditions. Benzene, vinyl
chloride, and phenol are relatively degradable, whereas the
chlorinated methanes and ethanes are not.
The silty sand layers above and below the clay layer contain
considerable organic material (8 percent), which increases the
sorption potential of organic contaminants. Subsequently, a
large fraction of contaminants with high organic carbon partition
coefficient (Koc) values, such as DEHP, will sorb onto the
sediments. Assuming that the partitioning of the contaminants
is currently at equilibrium, desorption of contaminants from the
soil will occur with extraction of contaminated ground water.
Contaminants with lower Koc values will desorb at a faster rate
than those with higher values. Initially, the rate of partitioning is
governed by mass action. Therefore, an increased rate of
extraction will enhance desorption until desorption becomes
rate limiting. The concentration of contaminants at which
desorption becomes rate limiting was estimated and is
discussed in Section A.7, in conjunction with indicator
chemicals.
A.6 Establishing Preliminary Cleanup
Levels
Contaminant-Specific ARARs and TBCs
Two kinds of contaminant-specific ARARs exist for several of
the contaminants detected at the site: Primary MCLs and
State Unacceptable Pollutant Levels (UPLs). MCLs exist for
eight of the contaminants detected at the Hypo-Thetical site,
and UPLs exist for five.
Table A-3 presents contaminant-specific ARARs and TBC
requirements applicable to the site. Cleanup
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Solvent
Recycling
Facility
Underground Storage Tank
Interior
Auto Cleaning
Facility
Abandoned Well
Ground-Water
Flow Direction
Legend
10Concentration, in ppb
H Soil Hotspot
Figure A-1. Distribution of Contaminants Hypo-Thetical
Site.
levels should be set for the following contaminants that exceed
these standards or criteria:
Benzene
DEHP
1,1-DCE
1,2-DCE
Iron
Manganese
Methylene chloride
Phenol
PCE
1,1,1-TCA
TCE
Vinyl chloride
Preliminary cleanup levels for benzene, 1,1-DCE, 1,1,1-TCA,
TCE, and vinyl chloride are set at the MCL level for protection
of health.
For iron and manganese, preliminary cleanup levels were set
at the secondary MCL level for protection of welfare (these
contaminants make drinking water taste bad). Since at
naturally occurring background
levels these metals were detected above the MCLs, it is not
necessary that the remedial action selected address these
contaminants. However, the treated effluent must meet the
POTWs pretreatment program requirements for these
contaminants.
The UPL level for DEHP was written 4 years ago. It is not
clear on what basis this standard was promulgated. It has
never been enforced because of the widespread presence of
DEHP at industrial areas throughout the state. For these
reasons, the remedial project manager for the Hypo-Thetical
site employed an ARAR waiver for the DEHP UPL and will
propose a cleanup level corresponding to the 10"6 risk level.
For methylene chloride and PCE, the State UPLs will be the
basis for the cleanup levels. For phenol, the preliminary
cleanup level will correspond to the RfD. For 1,2-DCE, the
preliminary cleanup level will be based on the lifetime health
advisory. When an MCL is promulgated, the cleanup level will
be reassessed and may be changed to reflect the MCL.
Assessing Aggregate Effects
Table A-4 presents estimates of the carcinogenic and
noncarcinogenic effects if the contaminants present at the
Hypo-Thetical site are remediated to the preliminary cleanup
levels. Aggregate carcinogenic risk is 2 x 10"4, and an
evaluation of the appropriate risk level will be made. For
noncarcinogenic effects, the hazard index is 1.2, and the
preliminary cleanup levels for the noncarcinogens will be
further reduced.
To attain a risk level of 10"6, the starting point for the
aggregate risk level for carcinogens, the preliminary cleanup
levels for key contaminants (those contributing most to the
aggregate risk level, i.e., 1,1-DCE and vinyl chloride) would
have to be reduced by a factor of 1,000 (i.e., 1,1-DCE to 0.007
ppb and vinyl chloride to 0.02 ppb). In evaluating whether
these levels should be used at the site the following factors
that indicate increased flexibility to use a less stringent
aggregate risk level were considered:
! The potential for human exposure from other
pathways is minimal; contaminated soil will be
remediated, and air emissions above health-based
levels are not anticipated
! There are no exposures above health-based levels
actually occurring at this time
! There are no sensitive populations or special
environmental receptors in the area around the site
i
Cross-media effects are not anticipated
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Table A-3
CONTAMINANT-SPECIFIC ARARs AND TEC REQUIREMENTS
HYPO-THETICAL SITE
All Values in ug/1
Chemical
Barium
Benzene
Bis(2-ethylhexyl) -
phthalate (DEHP)
Bromodichloromethane
Carbon disulfide
Copper
1,1-Dichloroethane (1,1-DCE)
t-l,2-Dichloroethane (1,2-DCE)
Di-n-butyl phthalate
Iron
Lead
Manganese
Methylene chloride
Nickel
Phenol
Tetrachloroethene (PCE)
1,1,1-Trichloroethane (TCA)
Trichloroethene (TCE)
Vinyl chloride
Zinc
Primary Secondary Proposed
(Health) (Welfare) MCLG MCLG
200
5
1
50
Toxicity
Protection
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Table A-4
AGGREGATE RISK
HYPO-THETICAL SITE
Chemical
Benzene
Bis-2-ethylhexylphalate
1,1-Dichloroethene
Methylene chloride
Phenol
Tetrachloroethene
1,1,1-Trichloroethane
Trichloroethene
Vinyl chloride
Preliminary Cleanup
Level
(ug/1)
Carcinogen
Classification
A
B2
C
B2
B2
B2
A
Excess
Li fetime
Cancer
Risk at
Preliminary
Cleanup
Level
DI/RfD at
Preliminary
Cleanup
Level
Exposure Assumptions:
Body weight = 70 kg
Drinking water ingestion rate = 2 I/
Exposure period = 70 years
Neg. = Negligible
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! The hydrogeology of the site is well defined and
ground-water flow paths can be estimated with
adequate precision
! Proven technologies will be used to remediate the
site
! The detection/quantification limits for 1,1-DCE and
vinyl chloride, even using available special
analytical techniques, do not permit measurement
of concentrations at levels corresponding to the 10"
6 risk level.
These factors suggest the selection of less stringent cleanup
levels. However, because benzene and vinyl chloride are
known human carcinogens, and because institutional controls
are not expected to be reliable, the appropriate aggregate risk
level is the 10"5 level. To attain a hazard index of 1.0 for
noncarcinogenic effects, the preliminary cleanup level for
phenol will be reduced to obtain a ratio of daily intake (Dl) to
RfD of 0.8. The concentration of phenol corresponding to this
level is 1,120 ppb.
In summary, the cleanup levels at the site are as follows:
! Benzene-5 ppb
! DEPH-51 ppb
! 1,1-DCE-0.7 ppb
! Methylene chloride-5 ppb
! Phenol-1,120 ppb
! PCE-25 ppb
! 1,1,1-TCA-200 ppb
! TCE-5 ppb
! Vinyl chloride-0.2 ppb
Special analytical services would be required to confirm
cleanup levels had been attained for 1,1-DCE and vinyl
chloride since these concentrations are below the practical
quantification limits achieved by standard procedures used in
the contract laboratory program.
These ground-water cleanup levels were also used to
determine the solid cleanup levels based on migration to
ground water. A leaching test was performed on the soil to
determine what residual contaminant levels could remain
onsite without contaminating ground water above health-based
levels.
A.7 Developing and Screening Remedial
Alternatives
Source Control Action
Soil contaminated at levels greater than 10,000 ppb (4,000
yd3) was excavated and incinerated offsite. A vacuum
extraction system was installed to remove the remaining
volatile organic compounds present at
greater depths to levels that would not pose a threat to the
ground water.
Selecting Indicator Chemicals
Indicator chemicals were selected to be used in the FS on the
basis of mobility and toxicity information (see Table A-5). Koc
values are known for 11 organic compounds. Contaminants
with low KQC values are more mobile than contaminants with
high KQC values.
These ground-water cleanup levels were also used to
determine the soil cleanup levels based on migration to
ground water. A leaching test was performed on the soil to
determine what residual contaminant levels could remain on
site without contaminating ground water above health-based
levels.
Because a localized TCE plume is emanating from the auto
interior cleaning area, TCE was selected as one of the
indicator chemicals. To predict movement of the contaminant
plume originating from the solvent recycling facility, indicator
chemicals were selected, as explained below:
! Benzene was detected at its highest concentration at
the border of the plume. Because of its unusual
occurrence (i.e., at the edge of the plume) benzene was
selected as an indicator chemical.
! 1,1-DCE was the most widely distributed chemical and
is relatively mobile.
i
PCE is relatively immobile and is widespread. It is
expected to be the most resistant to extraction.
! Vinyl chloride was widely distributed and is highly toxic.
On the basis of column studies conducted during the Rl, it
was determined that desorption is rate-limiting (and hence,
continuous ground-water pumping is not efficient) for the
contaminants in this particular soil when the concentrations
found in ground water are as follows:
TCE-20 ppb
Benzene-10 ppb
1,1-DCE-10ppb
PCE-50ppb
Vinyl chloride-10 ppb
Developing Remedial Alternatives
Area of Attainment. Since all source areas will actively be
remediated and no waste will be managed onsite as part of
the final remedy, the area of attainment will be the entire site,
including the source area.
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Table A- 5
CONTAMINANTS DETECTED IN GROUND WATER
CONCENTRATION, TOXICITY, AND MOBILITY
HYPO-THETICAL SITE
Chemical
VOLATILE ORGANIC COMPOUNDS
Benzene
Bromodichlorome thane
Carbon disulfide
Chloroethane
1, 1-Dichloroethene
Trans-1, 2-Dichloroethene
Methylene chloride
Phenol
Tetrachloroethene
1, 1, 1-Trichloroethane
Trichloroethene
Vinyl chloride
Phthalates
Bis (2-ethylhexyl) phthalate
Di-n-butyl phthalate
INORGANICS
Aluminum
Barium
Calcium
Copper
Iron
Lead
Magnesium
Manganese
Nickel
Potassium
Sodium
Zinc
aSamples in which the contaminant
bThe orcranic carbon = ma
Range of
Concentrations
Reported in Cleanup
Ground Watera Level
(/I) ('/I)
20 - 120 5
5-56
10-67
15 - 1,000
50 - 1, 900 0.7*
37 - 1,000 350
10-80 5
20 - 1,500 1,120*
45 - 650 25
12 - 1,500 200
6 - 1,200 5
45 - 500 0.2*
10 - 90 10
8-45
~
440 - 600
99 - 200
10,300 - 20,750
20-80
999 - 1,500
5-7
4, 000 - 7, 000
70-80
2-5
1,500 - 2, 000
6,550 - 10,000
32-50
was not reported are excluded.
contaminant/ka of oraanic carbon
Mobility
K b
Koc
(mloc/g)
83
-
54
65
59
8.8
6.2
364
152
126
57
170000
-
-
-
-
-
-
-
-
-
-
-
-
partition coefficient mg contaminant/liter of solution
^Cleanup level was reduced because of aggregate effects.
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Restoration Time Frame. To estimate the shortest possible
restoration time frame, a ground-water model was run several
times using various estimates of two parameters, porosity and
hydraulic conductivity, to predict the ground-water flow rate.
Estimated levels were based on data gathered when ground
water contaminated by the underground tank was pumped as
an interim action. It showed that the estimates of
ground-water flow were precise to approximately 50 percent.
The quickest feasible restoration time frame is estimated to
be 10 years, plus or minus 5 years. This rate is possible if
seven extraction wells pump at the maximum rate of
ground-water flow for 2 years and are then pulse-pumped for
approximately 8 years. Enhanced in situ biodegradation of
ground-water contamination will be initiated at the same time
as pulsed pumping. A second alternative using pulsed
pumping and enhanced biodegradation with three extraction
wells is estimated to restore ground water in 12 years plus or
minus 5 years.
Screening. Enhanced biodegradation alone was removed from
consideration during screening because it presented minimal
benefits over natural attenuation. Containment of
contaminated ground water was initially considered; however,
it was determined to be too costly and not feasible since the
site was expected to be developed.
Alternative Development. Table A-6 summarizes pertinent
information regarding the site.
The following three ground-water alternatives were developed
for detailed analysis:
! Alternative 1: Natural attenuation with monitoring-lf
the source is removed, natural attenuation is
predicted to eliminate the plume from the site within
40 years. However, the plume would simply migrate
and disperse downgradient of the site. The nearest
surface water body into which the plume could
discharge is approximately 1 mile away. Monitoring
would continue throughout the 40-year period. While
institutional controls would be effective onsite,
institutional controls downgradient of the site would
probably be unreliable.
! Alternative 2: Pump and treat with three extraction
wells-For some of the contaminants, the kinetics of
desorption from the soil matrix to the ground water
would be slower than the maximum pumping rate of
the ground water. For this reason, intermittent
pumping at three extraction wells was proposed.
Ground water would be pumped continuously for
approximately 2 years, and then a pulse/relax
cycle would be initiated. Ground water would be
treated using carbon absorption to meet required
pretreatment levels and discharged into a nearby
storm sewer. Enhanced biodegration would also be
used to attain health-based cleanup levels. This
alternative is predicted to achieve cleanup levels in 12
years, plus or minus 5 years.
! Alternative 3: Pump and treat with seven extraction
wellsThis alternative is similar to previous
alternative, except that treated ground water would be
reinjected to enhance contaminant movement. Again,
biodegradation and pulsed pumping would be used
after a period of continuous pumping to reduce
residual contamination to health-based levels. This
alternative is predicted to require 10 years, plus or
minus 5 years, to reach cleanup levels.
A.8 Detailed Analysis
The three alternatives were analyzed using the nine evaluation
criteria. The natural attenuation alternative was rejected
because it is only marginally protective and does not reduce
mobility, toxicity, or volume. The State was also opposed to
this option because of the need for long-term access
restrictions of ground-water usage in the area.
Both pump and treat alternatives are protective and meet all
ARARs. However, the more aggressive seven-well pump and
treat alternative may be less flexible for incorporating design
changes as additional information on pumping influence is
obtained. If the wells are not placed in optimal areas, more
wells may have to be added. By starting with a smaller
number of wells and supplementing the system as information
is obtained, a more cost-effective remedy may result. In
addition, the seven-well pump and treat alternative is more
expensive. Although the seven-well pump and treat alternative
is predicted to reach cleanup levels faster than the three-well
alternative, the uncertainty of the effect of reinjection makes
the remedy less reliable. It was determined that the three-well
alternative should be implemented on the basis of its overall
balance of the evaluation criteria. At the end of 1 year, the
performance of this alternative will be evaluated, and if its
performance is poor, the alternative will be upgrade with
additional wells and possibly a reinjection well. Table A-7
summarizes the pertinent considerations relating to the five
criteria that were balanced.
Additional action-specific ARARs with which the selected
remedy must comply are listed below:
! The County POTW's pretreatment program is
applicable to discharge of the treated water to the
sewer system
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Table A-6
HYPO-THETICAL SITE SUMMARY
Type of SiteIndustrial landfill, underground solvent
storage tank
Local Land UseResidential
Ground-Water UseUpper aquiferpotential drinking water
source; lower aquifercurrent drinking water source; 50
wells in the area; some screened through both aquifers;
municipal supply available
Soils--VOC contamination; hot spot of 4,000 yd3; low-level
contamination of 20 acre-feet
Ground-Water Response Objectives
" Prevent exposure to contaminated drinking water
" Prevent contamination of deeper aquifer
" Restore contaminated ground water for future use
Soil Response ObjectivesPrevent risk from soil ingestion,
prevent contamination of ground water.
Data Needed
" Wells and piezometers in deep and shallow aquifers
to determine extent of contamination
" Saturated zone soil contaminant concentrations and
TOC to determine partition coefficient
" Aquifer pump test to determine hydraulic
conductivity and estimate capture zones
" Contaminant degradation information
Removal/Interim Action TakenRemove tank and surrounding
soils; vapor extraction, and ground-water pumping; seal
abandoned well
ARARSNine MCLs and Five State UPLs
Ground-Water Remedial Alternatives
" Natural attenuation
" Two pump and treat scenarios
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Table A-7.
Summary of Detailed Analysis Hypo-Thetical Site-Balancing Criteria
Alternative
Short-Term
Effectiveness
Long-Term
Effectiveness
Reduction of Mobility,
Toxicity, or Volume
(MTV)
Implementability
Present
Worth Cost
Natural attenuation
Pulsed pumping, 3 well
points, air-stripping,
enhanced biodegradation
Pulsed pumping, 7 well
points, air-stripping,
reinjection, enhanced
biodegradation
Presents a higher risk
to the community
over the short-term;
does not cause
exposure to workers;
does not cause
environmental
impacts, restoration
time frame is 40
years
Reduces risk to the
community over the
short-term; potentially
small exposure to
workers; does not
cause environmental
impacts, restoration
time frame is 12
years.
Reduces risk to the
community over the
short-term; potentially
small exposure to
workers; does not
cause environmental
impacts; restoration
time frame is 10
years
Potential for exposure from
residual contamination
because institutional controls
such as deed restrictions are
not effective. Risk for
carcinogens is at the high end
of the protective risk range
(2x10'4) and the HI is
above 1.0.
Residual risk is 10'5 for
carcinogens, and the HI for
systemic toxicants is 1.0
Regional risk is 10~5 for
carcinogens, and the HI is 1.0
No treatment; no
destruction; no reduction
of MTV; residual
contamination is high
Contaminants are treated;
quantitative residual
contamination
is below cleanup levels
Contaminants are treated,
residual contamination is
below cleanup levels
Deed restrictions are $500,000
unreliable; ease of taking
additional actions is high;
ability to monitor is high;
ability to obtain approvals
from other agencies is high;
no coordination problem
Biodegradation may not $3,000,000
work, ease of undertaking
additional actions is good;
ability to monitor is high;
other approvals can be
obtained; coordination with
other agencies is moderate
Biodegradation may not $5,000,00
work; ease of undertaking
additional actions is poor,
ability to monitor is uncertain
because of difficulties in
predicting the effect of
reinjection; approval of
underground injection is
questionable; coordination
with other agencies is
moderate.
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! The State air toxics regulations are applicable to
air-stripping.
A.9 Variations in Site Conditions
Variation 1: Surface Water
If a stream had been on the site and contaminated ground
water currently or potentially discharged to the stream,
potential exposure pathways related to surface water would
have been identified. These would have included the following:
! Direct contact with contaminated surface water for
people swimming and playing in the stream either at
the site or downstream of it
! Ingestion, by humans, of aquatic organisms that have
become contaminated through bioconcentration or
ingestion of contaminated surface water
! Ingestion and bioconcentration of contaminated
surface water by aquatic organisms
! Ingestion, by terrestrial organisms, of aquatic
organisms that have become contaminated through
bioconcentration or ingestion of contaminated surface
water
Response objectives related to surface water would also be
identified and would include preventing exposure to
contaminated surface water and contaminated aquatic
organisms, protecting environmental receptors, and restoring
contaminated surface water.
Additional data collection would include taking surface water
and sediment samples upstream and downstream of the site.
If contaminants were found in the surface water or sediments,
samples of edible fish portions would be taken to determine if
aquatic organisms were being affected.
Regardless of the analytical results of these samples, an ACL
under CERCLA Section 121(d)(2)(B)(ii) would not be
considered at this site because institutional controls
preventing exposure to contaminated ground water would not
be reliable enough to ensure that wells would not be
constructed in the upper aquifer or to the lower aquifer without
preventing cross-contamination. If necessary, access to the
surface water in areas where contaminant levels exceed
standards would be restricted, and signs warning that fish
may be contaminated would be posted.
Cleanup levels would be determined on the basis of standards
and criteria for drinking water consumption, WQC for fish
ingestion and drinking water ingestion, and WQC for effects to
aquatic organisms. These are shown in Table A-8.
A comparison of the WQC in Table A-8 to the cleanup levels
presented in Section A-6 indicates
that a cleanup level for copper would be determined on the
basis of aquatic effects. Otherwise, cleanup levels would not
be changed.
Variation 2: Class I Ground Water
If the ground water had been Class I, i.e., if no alternate
supply were available and the plume had reached nearby
residents' wells, a removal action consisting of wellhead
treatment would have been implemented. An interim action
consisting of wellhead treatment would be completed if levels
in the wells did not reach removal action trigger levels but
were contaminated above health-based levels. Wellhead
treatment would probably involve carbon absorption because
of the nature of the contaminants. This treatment would be
less intensive than air stripping with respect to operation and
maintenance. Because the time frame would have more
significance, the seven-well alternative would be chosen.
Since this alternative involves recharge of treated ground water
it has the added benefit of preserving the resource, in this
case, an important consideration under the short-term
effectiveness evaluation criteria.
If the plume had not yet reached the wells but was projected
to reach them within 2 to 3 years, an interceptor well or trench
would be constructed near the leading edge of the plume,
early in the RI/FS process. This would prevent the plume from
reaching the wells while the RI/FS was being completed and
the final remedy was being selected. The well or trench would
be pumped to maintain contaminant concentrations below
health-based levels and would have only minimal effect on
plume movement. These actions would be coordinated with
the operators of the private and municipal wells. Another
option that might be considered would be alternating pumping
patterns at the existing wells to limit the extent of any plume
expansion.
Variation 3: Class III Ground Water
If the total dissolved solids (TDS) concentration at the site
exceeded 10,000 milligrams per liter, the ground water would
not have been usable as a drinking water source. If the ground
water was not interconnected to the drinking water aquifer and
not interconnected to the drinking water aquifer and did not
discharge to a stream, the ground water at this site would not
have served any other beneficial uses, such as irrigation, and
so it would have been classified Class III. Natural attenuation
would have been the selected alternative. However, if the
ground water discharged to surface water, protection of
aquatic organisms would have been a remedial response
objective. In this case, cleanup levels would have been
established to prevent effects to aquatic organisms.
If the ground water was found to be interconnected to a
drinking water aquifer, cleanup levels would be determined on
the basis of health-based levels attained at the point of
interconnection. Although natural attenuation may be
appropriate in this case, it
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Table A-8
HEALTH-BASED CRITERIA RELATED TO SURFACE WATER
HYPO-THETICAL SITE
Chemical
WQC for Protection
of Human Health
Drinking Water and
Fish Ingestion, ppb
Benzene
DEHP
Chloroform
Copper
Dichloroethenes
1,2-DCE
Iron
Manganese
Methylene chloride
PCE
1, 1,1-TCA
TCE
Vinyl chloride
10,
18,
0
000
0
0
0
300
50
0
400
2
2
.66
.19
.033
.94
.8
.7
(C)
(S)
(C)
(C)
(C)
(S)
(S)
(C)
(C)
(C)
(C)
WQC for Protection
of Aquatic
OrganismsFresh
Water Organisms, ppb
5300 (a)
1240 (c)
12 (c)
11600 (a)
20000 (c)
1000 (c)
840 (c)
21900 (c)
a = Acute effects
c = Chronic effects
C = Carcinogenic effect (lxlO~6 excess lifetime cancer risk)
S = Systemic toxic effect
would be critical to ensure that wells constructed in the
deeper aquifer would not enhance chemical movement from
the shallow to the deeper zone. This could be accomplished
by enforcing a requirement that any new wells be
constructed with a seal in the upper portion of the well.
Variation 4: Complex Hydrogeology
If the shallow aquifer had been in a low permeability
formation, it is possible that ground-water extraction using
extraction wells would not have been feasible. Trenches,
French drains, or well points would have been considered to
extract ground water. Alternatively, dewatering the shallow
aquifer and using vapor extraction could have been
considered.
If the site had been in karst terrain, data collection activities
would have been different than for other types of aquifers. A
dye tracer study to determine ground-water conduits in the
subsurface would have been considered.
Variation 5: Inorganic Contaminants
If contaminants at the site had included metals, additional
treatment options would have been considered.
Biodegradation or air-stripping probably would not have been
feasible, and contaminant would not have been acceptable
because of the development pressures at the site. The
remedial alternatives that would have been analyzed in the
detailed analysis would have involved ground-water
extraction and treatment, possibly using ion-exchange or
precipitation. Because metals are relatively immobile and
inhibit biodegradation, the restoration time frame would have
been longer. A technical feasibility waiver would be used, if
necessary, for residual contamination that remains above
health-based levels. Restrictions on well construction, as
described in Variation 3, would be implemented for the area.
In addition, ground water downgradient from the plume and
upgradient from any active drinking water wells would be
monitored as a warning system to prevent chemical
migration to the wells.
Variation 6: Reliable Institutional Controls
If institutional controls such as requiring new well permits or
restricting access to the aquifer were more reliable, a
remedy relying on institutional controls such as natural
attenuation would still not be selected, because a feasible
and implementable remedy is available, and the aquifer is a
potential drinking water source. However, if the ground water
discharged to nearby surface water and the resulting
contaminant levels in the surface water were not statistically
significant, an ACL, as described in Section 4.5, would be
considered.
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Appendix B
Strategy for Addressing Ground-Water Contamination from Multiple Sources
Involving Superfund Sites
The Office of Emergency and Remedial Response (OERR) has
developed a strategy for ways in which the Superfund program
can address ground-water contamination from multiple
sources (National Priorities List (NPL) sites and other
sources). The strategy presents an approach for determining
when an alternate water supply should be provided, what type
of source control and ground-water response actions should
be taken, and implications of this strategy for listing and
deleting sites from the NPL.
The flexible approach presented in this strategy is an initial
step toward the development of more detailed guidance as the
program gains experience with such situations.
Exhibit B-1 presents an example of a multiple-source plume.
Superfund Remedial Strategy for
Ground-Water Contamination from
Multiple Sources
Purpose
This strategy presents an approach for addressing
ground-water contamination at sites contaminated from
multiple sources, including sources on the NPL. This strategy
is an initial step toward the development of more detailed
guidance as the Superfund program gains experience with
such situations.
Background
The goal of CERCLA and its related regulations, standards,
and criteria is to protect human health and the environment.
The objectives of the Superfund program are consistent with
this goal.
The Superfund program is now confronting numerous issues
and problems involving NPL sites associated with
ground-water contamination caused by multiple sources such
as the Biscayne Aquifer and South Valley, New Mexico.
Current Superfund responses to multiple source ground-water
contamination problems would provide for cleanup and control
of
CERCLA priority releases only. Releases from sources not
addressed by CERCLA could continue to contaminate the
general area, making Superfund remedial action less effective.
To obtain an effective remedy for ground-water contamination
caused by multiple sources, the response actions must be
broader in scope and involve organizations and authorities
outside the Superfund program.
Given the potential magnitude of multiple source ground-water
contamination problems and the fact that Superfund resources
are finite, the Superfund program needs to adopt a strategy
that will set priorities and establish a sequence of remedial
and enforcement actions that will appropriately address these
problems. A fully effective response generally will involve the
Superfund program working with other involved parties to
clearly define their respective remedial roles and
responsibilities. This recommended approach should be
consistent with other environmental laws.
Overview of Approach
This approach proposes that the Superfund program work
cooperatively with other responsible entities to achieve
comprehensive remedies at multiple source ground-water
contamination sites but accept primary responsibility for
coordinating all involved parties during the source identification
phase of work.
The Superfund program should begin its coordinating effort
once multiple source ground-water contamination is
suspected. The program should coordinate an initial scoping
plan for source identification that would include limited
sampling. Locations of possible sources may be determined
through two surveys: (1) a survey of contributors to and users
of the affected ground water (termed a contributor/user
assessment) that will help identify the other parties that must
be involved in the formulation of an effective remedy; and (2) a
survey of potential sources such as solvent storage facilities
located at or upgradient of the area of contamination. Often,
a local agency has the necessary resources to complete
these surveys, and the role of the
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Exhibit B-1.
A Multiple Source Plume in the Biscayne Aquifer
The Biscayne aquifer, a highly permeable limestone and sandstone aquifer, is the sole underground source of drinking water for 3
million residents of southeast Florida.
Three Biscayne aquifer Superfund sites were identified in Dade County. Because the three sites affect the same general area of
the aquifer, they are treated as one "management unit." The three sites include the Varsol Spill site, the Miami Drum site, and the 58th
Street Landfill. Ongoing spills from other sources also contaminate the aquifer.
During the preliminary assessment/site inspection, EPA took a lead role in coordinating response to the contamination problem because
the Superfund sites were believed to be the primary contributors to the ground-water contamination. An extensive study to
characterize the affected area of the Biscayne aquifer has been completed.
At the Varsol Spill site, it was determined that there are no longer any traces of soil contamination at the site. Presumably, the
contaminants volatilized. A ROD proposing no source control actions was signed in 1985. At the Miami Drum site, extensive
contamination was found. Excavation and offsite disposal of contaminated soil was recommended as an operable unit in a ROD
signed in 1982. An enforcement decision document for the northwest 58th Street landfill was completed in 1987 and proposed
closure of the landfill and provision of an alternate water supply to residents near the site who use private wells.
The ground-water remedy proposed for the Biscayne Aquifer Superfund Site ROD that was signed in 1985 includes adding
air-stripping to the existing water treatment systems and operating additional municipal wells to recover contaminated ground water
and provide potable water.
Other agencies that have been involved in the effort include:
The State Department of Environmental Regulation
The State Department of Health
The Agency for Toxic Substances and Disease Registry
The Dade County Department of Environmental Resources Management
Two adjacent counties
These agencies formed a Technical Advisory Committee (TAG) that made decisions through consensus management. In addition to
working on Superfund-related issues, the TAG also put together the Biscayne Aquifer Protection Plan, a 20-point plan devised to
prevent additional contamination of the aquifer. The provisions of this plan include such items as regulating land use, regulating
storage tanks, adopting emergency spill provisions, recycling oil, and ground-water monitoring. Now that the studying and planning
phases have been completed, the TAG meets less frequently.
The Dade County Department of Environmental Resources Management is a well-established organization with considerable
professional talent. It receives no Federal money for this effort. The State's role is relatively limitedthe State's water management
districts and development plans must be consistent with the Protection Plan.
Superfund program staff is to maintain coordinating and
support functions.
Superfund will implement appropriate remedial actions
related to NPL sites once an RI/FS is completed. At this
point, the Regional Administrator, in consultation with the
Assistant Administrator of the OSWER, should evaluate
the appropriateness of the Superfund program, retaining
primary responsibility for coordinating the ground-water
response action for all sources. This decision may be
determined by factors such as the contribution of Superfund
sources relative to other sources, as well as the availability
and willingness of other involved parties to initiate action.
If the Superfund program does not take the lead
responsibility, the program will work in cooperation with
other involved parties to formulate and implement
an effective solution to the multiple source ground-water
problem. If the Superfund program retains lead
responsibility, it will work with the other involved parties to
develop a multiple source ground-water response plan,
which would include written commitments from each party
to take specific remedial actions that, when combined,
would result in an effective remedy for the entire ground-
water contamination problem. An appropriate community
relations program will be conducted throughout this
process.
Challenges Associated with Ground-Water
Contamination Caused by Multiple Sources
If ground-water contamination has occurred because of
multiple sources, remedial decisions become more
complex. Some of the many technical, administrative, and
financial considerations that may result when
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multiple source ground-water contamination exists are as
follows:
! Greater technical difficulty of remedial action may
result from complex mixtures of hazardous
constituents.
! The effectiveness of institutional controls may
decrease because of multiple land owners.
! Applicability and responsibility of other statutory and
regulatory authorities may be increased.
Table B-1 lists the types of sources that may potentially
contaminate ground water but may not be CERCLA-priority
releases.
Table B-1. Potential Sources of Multiple Source Ground-Water
Contamination
1. Major Point Sources
! Abandoned hazardous waste land disposal units
! Industrial NPDES facilities
! Municipal NPDES facilities
! Land-spreading of municipal sludge
! Non-regulated holding ponds for industrial waste
(including mine tailings)
! Air pollution (smelter operations, etc.)
! RCRA-permitted TSD facilities
! Federal Facilities
! State-lead sites that have been deferred from
listing on the NPL because of state action
! Abandoned dry wells
2. Non-Point Sources
! Agricultural runoff (infiltration)
! Urban runoff (infiltration)
! Air Pollution (acid rain)
! Irrigation return
3. Multiple Point Sources
Underground storage tanks
Fuel spills
Commercial establishments (e.g., laundries)
Septic tanks
Sewer exfiltration
Listing Sites and Determining Response Approach
A specific preliminary assessment/site investigation (PA/SI)
work plan may be expanded when ground-water contamination
is found in significant amounts in wells upgradient of the
source being investigated. The detection of contaminants in
the upgradient wells suggests multiple source ground-water
contamination.
The Superfund program should be responsible for coordinating
the expanded PA/SI activities. This leadership role would
entail assigning responsibility for obtaining data.
To identify sources of contamination and to list potential
sources as priorities for undertaking enforcement activities,
it may be necessary to consider the contribution of the
source to the overall ground-water contamination problem as
well as the planned sequence of remedial actions. A list of
potential sources should be assembled on the basis of site-
specific information. Such information could include the
volume of chemicals used by each potential source and the
locations of the sources relative to the site. Once the list of
potential sources has been assembled and it has been
determined which sources are most likely to have affected
ground water, a limited sampling program can be instituted.
Sampling programs for the source identification may be
coordinated by the Superfund office.
It is important that sampling programs conducted by or under
the direction of agencies other than EPA also follow a valid
QA/QC plan. Quality-assured data can be used to prove
liability for ground-water remedial actions. Even cooperative
potentially responsible parties (PRPs) should follow strict
QA/QC procedures to ensure reproducible results and
because their data are open to challenge from other PRPs
when the plume is from multiple sources.
After potential sources have been identified, activities may
include, but are not limited to, identifying the following:
! Targets for PA/SI work
! Areas for NPDES compliance inspections and
possible permit tightening
! Areas for intensified RCRA inspection
! Areas for Toxic Substances Control Act inspection
! Areas in which State environmental programs should
be examining permits, inspecting for compliance
with their regulations, and upgrading permits, where
needed
! Areas in which the State and local health
departments should be inspecting for compliance
with their regulations
i
Local inspections by county and city organizations
to ensure compliance of and adequate coverage by
their regulations
Source identification efforts should be scheduled before the
RI/FS is begun for any interim actions or operable units. To
the extent possible, PRP-lead RI/FSs and removals should
be used. Before the ROD is signed for the first operable unit,
it is important that the enforcement case be developed.
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This is particularly important if the cost of the operable unit is
high.
Priorities for enforcement activities that pertain to multiple
sources should be based on the severity of release from each
source. If more than one source is on the NPL, the program may
consider combining the RI/FSs for these sites, if appropriate.
Another possible approach for the investigation phase, which
has been used in some of the regions, is to require investigation
under RCRA authority as specified in Section 3013 of RCRA.
Under this authority, EPA can order the owner/operator of a
facility at which hazardous waste is or has been treated, stored,
or disposed, to perform monitoring, testing, or analyses
necessary to determine the nature and extent of a potential
hazard at the site to human health and the environment. Also,
if contaminated ground water discharges to a navigable stream,
using the enforcement authority under the CWA should be
considered.
Major Remedial Options for Sites Associated With
Contaminated Ground Water
Three types of remedial actions are considered at sites with
ground-water contamination from a single source:
! Provision of alternate water supplies (including wellhead
treatment)
! Source control measures
! Ground-water remedies
These three types of actions may involve similar components.
The first decision at a site will be whether to provide an alternate
water supply. Ideally, the source control remedy and the
ground-water remedy decisions should be made simultaneously
to obtain the most cost-effective remedy for the site. It may not
be possible, however, to make these decisions together at sites
in which multiple sources contribute to ground-water
contamination.
Alternate Water Supply
Public health is endangered when contaminants in drinking
water supplies exceed health-based limits. Public health
protection can be ensured with the provision of an alternate
water supply that could include a wide range of actions, such as
wellhead treatment, well relocation, selective use of wells,
connection to an existing system or surface water source, and
so forth.
An alternate water supply will be provided with Superfund
resources if an NPL site is found to be a significant contributor
to the contaminated drinking water source. The NPL site might
be considered a significant contributor if the type of
contaminants from the site are detected at a receptor point.
Specific trigger levels and a methodology for determining
whether a potential drinking water threat exists have been
developed by the Superfund program (U.S. EPA, 1987f,
1987J).
In addition, Superfund resources will be used to provide an
alternate water supply if the need to alleviate the public
health threat posed by contaminated drinking water
outweighs the need to identify and quantify all contributing
sources.
Source Control
Actions taken to minimize or prevent the spread of
contaminants from the source are termed source control
actions. These types of actions include source removal, in
situ treatment, and containment. In general, the Superfund
program seeks to prevent or minimize all source releases to
protect public health and the environment.
It is preferred that the Superfund program make a remedial
decision for an NPL site that concurrently addresses source
control and ground water. However, the length of time
required to formulate a final ground-water remedy for all
sources by obtaining written commitments from other
involved parties (possibly through lengthy negotiations) and
for developing a multiple-source ground-water response plan
may require that an interim source-control measure or an
operable unit for an NPL site be implemented. This interim
remedy would be designed to minimize further source
migration while a multiple source response plan is being
developed.
The final source-control decision could be delayed until the
ground-water remedy is selected. The advantage of this
recommended approach is that source migration is
temporarily minimized until the final ground-water decision is
made. Thus, Superfund resources generally would not be
used for more permanent source control remedies unless
such actions are necessary and effective. The disadvantage
of this approach is that a more permanent remedy may be
more difficult to implement (retrofit) if an interim measure has
already been implemented. This factor must be evaluated to
determine whether an interim source-control measure should
be implemented.
Ground-Water Remedies
When ground-water contamination is caused by multiple
sources, the amount of resources Superfund is willing to
commit to the ground-water remedy will be derived in large
part from the extent to which contamination from NPL sites
contributes to the total ground-water problem. This is often
difficult to determine and may have to be estimated or
negotiated. The willingness and capability of the other
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involved parties to take actions to address contamination for
which they are responsible may also be a factor in determining
resource allocation.
Schedule
The following factors should be balanced when scheduling
operable units at multiple source ground-water contamination
sites:
! Remedial action priorities (see Chapter 3)
! Enforcement priorities
- Timing of field investigations to develop the
enforcement case
- Additional data needs for enforcement
- Timing of operable units
- Relative costs of the operable units
Remedial action priorities take precedence over enforcement
priorities. However, enforcement actions can improve the
timeliness and extent of overall site remediation.
The following remedial action activities should support the
enforcement function to the extent practicable:
! Setting schedules for operable units
! Collecting data for remedial action evaluation or design
! Identifying sources
As mentioned previously, a multiple-source ground-water
response plan should be developed to define the appropriate
ground-water remedy. This plan would also detail specific
actions to be taken by each party. If participation by other
entities is essential to effective ground-water remediation, the
Superfund program will not implement its portion of the selected
remedy unless the other entities commit to implementing their
own remedial actions. Superfund enforcement authority should
be considered when cooperation is not voluntary. The elements
of a multiple-source ground-water response plan include:
! Summary and analysis of contributor/user assessment
(performed in part for the source-control decision)
! Goals for ground water (use, value)
! Available restrictions on ground-water uses:
- Ban on new drinking water wells unless adequate
pretreatment is provided
- Closure of existing wells unless adequate
pretreatment is provided or notices are posted
- Restriction of industrial/agricultural uses, as
necessary
! Control plan for existing regulated sources:
- RCRA facilities
- NPDES industrial discharges
- Small businesses
- Non-point and multiple point sources, e.g.,
underground storage tanks, small commercial
enterprises, septic tanks, agricultural runoff
! Control Strategy for all other sources contributing to
areawide ground-water contamination:
- NPL-Enforcement- and Fund-lead
- Industrial discharges
- Small businesses
- Non-point sources
! Definition of roles and responsibilities, and a
schedule for action by:
- Individual parties
- Federal, State, and local authorities
! Written commitment to take designated remedial
action by all involved parties
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Appendix C
Documenting an Interim Action
The ROD justifying an interim action is less detailed than a
ROD for a final remedial action. In particular, fewer alternatives
are considered because, in most cases, the decision that a
particular scope of the interim action would be beneficial is
based on best professional judgment. The five statutory
findings discussed in Section 2.2 must be made; however, the
discussions should be limited to the scope of the interim
action itself. For example, an interim pump and treat system
might be instituted to limit contaminant migration, even though
health-based levels in the ground water will not be met.
Institutional controls to prevent consumption of such ground
water should accompany the interim action. In addition, the
nine criteria should be evaluated to compare a limited number
of alternatives. The ROD should contain the following
sections:
A statement of the problem
The objectives of the remedy
The alternatives briefly evaluated using the nine
criteria and the reasons for selecting the alternative of
choice
Statutory findings
A responsiveness summary
Statement of the Problem
This section of the ROD describes the reason for
implementing an interim action. If an interim action is
implemented to reduce plume migration, characteristics of the
plume are described. If an interim action is implemented to
reduce exposure, the affected population is identified, and the
concentrations of the contaminants of concern are listed.
Objectives of the Remedy
This section states how an interim action responds to the
problem. It also describes the relationship between the interim
action and final remediation.
Alternatives Evaluated and Rationale for Selecting the
Interim Action
A limited number of alternatives is described and evaluated on
the basis of their ability to meet the objectives of the interim
action. The selected interim action is justified following a brief
discussion of the nine evaluation criteria (presented in Chapter
6) and the benefits of taking the action. (See Table A-2 in the
case study for an example of this evaluation.) In addition, the
following points should be made:
The interim action is necessary or appropriate to
stabilize the site, control the source, prevent further
degradation, prevent exposure, or otherwise
significantly reduce threats to human health and the
environment.
The interim action will not exacerbate the site
problem.
The interim action is consistent with the final remedy.
There is a commitment to evaluate additional
information and select a final remedy within a
specified time frame.
Statutory Findings
The five statutory findings presented below are evaluated with
respect to the proposed action, and a demonstration of their
consistency within the scope and goals of the overall remedy
is presented. In some instances, however, such as when an
alternate water supply is provided, some statutory
requirements (such as reduction of mobility, toxicity, or
volume) may not be pertinent to the scope of the action. The
five statutory findings include:
Protection of human health and the environment-The
remedy is shown to be protective in relation to the
stated goals of the action. Human health and the
environment must be protected during
implementation, and the remedy must mitigate or
fully control risks for
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the site problem that is addressed by the action. For
example, an alternate water supply must prevent
exposure to ground-water contamination, but it need
not address other threats from the site; an interim
action that contains the plume need not remediate
ground water. As appropriate, interim actions can be
justified by the need to take rapid action. Short-term
effects from residual contamination or effluent
disposal are also addressed.
Attainment of /AR/ARs-Action-specific ARARs that
pertain to the interim action technology are identified,
and it is shown that ARARs related to the treatment
and disposal of effluent, for example, are met. ARARs
pertaining to the storage of hazardous waste may be
waived using the interim remedy waiver, which is
described in Chapter 6. Other ARARs relating to
short-term effectiveness and protectiveness of the
remedy, however, generally cannot be waived.
Cleanup levels for the site typically are not
established since interim actions are not final. Thus,
an interim ground-water action need not achieve
chemical-specific ARARs in ground water.
Cost-effectiveness -Capital, O&M, and present-worth
costs are presented. In addition, it is shown that the
costs of the
interim action are proportional to the effectiveness of
the action.
Use of alternative technologies and permanent
solutions to the maximum extent pracf/caJb/e-This
finding is discussed in the context of the overall site
management strategy as well as for the interim
remedy itself. The reason for implementing an interim
action is presented, along with a showing that the
interim action is consistent with the final remedy. The
need for quick action becomes a factor when
determining if a treatment technology is practicable.
Reduction of mobility, toxicity, or volume-Interim
actions designed to address hot spots or prevent
plume migration through treatment meet this criterion,
while those that reduce exposure to contaminants
generally do not. For example, pump and treat
actions reduce the volume of contaminated
groundwater, while alternate water supplies do not
reduce mobility, toxicity, or volume.
Responsiveness Summary
The responsiveness summary of the ROD summarizes the
problem and its mitigation and provides responses to
comments received from interested parties. A summary of the
statutory requirements and how they are met is also included.
C-2
Word-searchable Version Not a true copy
-------
Appendix D
Basic Ground-Water Equations
This appendix presents two models that can be used to
estimate the time required to restore the water and soil in a
contaminated aquifer to the desired cleanup level for a given
chemical. The first model, the batch flushing model, is based
on a series of consecutive discrete flushing periods. Each
flushing period consists of enough clean water, introduced at
a known rate, to fill the pore space in a given volume of
aquifer. Values of contaminant concentration for both soil and
water are calculated following each flushing period. The
second model, the continuous flushing model, enables values
of concentration to be calculated at any arbitrary time
increment, regardless of the volume of water flushed through
the aquifer.
Batch Flushing Model
The soil contaminant concentration for any flush, i, can be
calculated from the following equation:
Cs(i) =
(1)
where:
Cs(i)
n
pb
the soil total volatile organics (TVO)
concentration after i flushes, mg/kg
the concentration of TVO in the water in
equilibrium with the soil, mg/l
the porosity of the soil
the bulk density of the soil, mg/l
Once the soil TVO concentration is calculated, the TVO
concentration in the ground water is calculated by the
following formula:
Cs,..
(2)
where:
= distribution coefficient
Once equation (2) is evaluated, the value for Cw(i) can be
entered into equation (1) as Cw(M) to calculate the soil
concentration after the next flush. This is repeated until the
soil and ground water reach the desired concentrations. The
time required for each aquifer flush is obtained by dividing the
control volume by the pumping rate, and the number of flushes
can then be converted into the time required for restoration. It
should be noted that soil and ground-water concentrations are
related and cannot be independently set because the model
assumed equilibrium concentrations for both phases.
Several assumptions are inherent in the use of this model:
! The total mass of contamination is in chemical
equilibrium between the solid (soil) and the liquid
(ground-water) phase.
! The use of Kd implies that the adsorption/desorption
isotherm is linear. Equation (2), however, can be
replaced by any nonlinear isotherm function as long
as the chemical equilibrium assumption is not
violated.
! The concentration of the contaminant in the water
used to flush the aquifer is less than or equal to the
desired cleanup level, and regardless of
concentration, this level remains constant during the
entire flushing process.
! No other chemical reactions occur that interfere with
the adsorption/desorption process.
For the particular case described in Figure D-1, calculations
based on this model yield a value of 27 years for aquifer
restoration to a level of 80 ppb TVO. Note, the solution plots
as a straight line because Equation (2) is linear.
Continuous Flushing Model
In this model, ground water is continuously pumped out of the
control volume into the treatment system, and the treated
water is continuously recharged to the control volume. This
process acts to dilute the ground water. The pumping flow rate
multiplied by the concentration of the contaminants in the
ground water will yield the mass of VOCs pumped out in a
given time interval. The mass of VOCs leaching into the
ground water from the soil is a function of the
D-1
Word-searchable Version Not a true copy
-------
leaching rate constant developed from the leaching column
study. The time increment, t, was arbitrarily set at 1 day. The
model recalculates a new soil and ground-water contaminant
concentration for every day of pumping. The equations for the
model can be written as follows:
Ground-water VOC =
mass at time t
Ground-water VOC
mass at time(t-1)
- Mass of VOCs pumped out
+ Mass of VOCs leached
into ground water from soil
1000,000
VOC in 1-000
Ground-Water
100
(3)
80 ppb in 27 years
0 10 20 30 40 50 60
Number of Flushes
0 6.3 12.5 18.8 25.0 31.3 37.5
Years
Figure D-1. Prediction of Ground-Water Restoration
Time Frame Using the Batch Flushing Model
Mw
(t)
(5)
Best fit curve from data is
C/Co = exp (-0.0872 x PV)
where:
C = concentration of soil contaminants
Co = initial concentration of soil contaminants
PV = pore volumes of water flushed through soil column
vDynamic Leaching Rate Constant = 0.0872 1 /PV
where:
Mw(t) = mass of VOC in ground water at t, kg
Mw(H) = mass of VOC in ground water at the
previous day, t-1, obtained from the previous
day's calculation, kg
Q = ground-water pumping rate, 1/day
Cw(f> = concentration of VOCs in ground water, kg/I
T = time period of one iteration, which is set
to 1 day
Ml(tt.1} = mass of VOCs that leach out from the soil
and into the ground water from the time
interval from (t-1) to (t), calculated from a
first-order decay equation using the dynamic
leaching rate constant derived from the
laboratory data shown in Figure D-2, kg
V = control volume of aquifer, D-2
By using this model, a prediction of 9 years for the restoration
time frame for the site was obtained, as seen in Figure D-3.
5 10 15 20 25
Pore Volumes of Flushing Water
30
Figure D-2.
Results of Leaching Column Study for
Determination of the Dynamic Leaching
Rate Constant
1000,000 -T
VOC in 10,000
Ground-Water
1,000
100
80 ppb in 9 years
Figure D-3.
8 10 12 14 16 18 20
Years
Prediction of Ground-Water
Restoration Time Frame Using the Continuous
Flushing Model
D-2
Word-searchable Version Not a true copy
-------
Appendix E
Tables of U.S. EPA Water Standards, Criteria, and Guidelines for Establishing
Ground- Water Cleanup Levels
E-1
Word-searchable Version Not a true copy
-------
Table E-l
U.S. EPA DRINKING WATER STANDARDS, CRITERIA, AND GUIDELINES FOR PROTECTION OF HUMAN HEALTH
All values presented in this table must be confirmed
As of August 1, 1988
(ug/1)
Hater Quality Criteria for Protection of Hunan Health(g)
Practical
Quanti-
fication
Chemical
Acenaphthene
Acenaphthylene
Acetone
Acraleln
Acrylanlde
Acrylonltrlle
Alachlor
Aldicarb
Aldrln
Aluulnua
Anthracene
Antimony, total
Arsenic, total
Asbestos
Barium, total
Benzene
Benzldlne
Berao (a) anthracene
Benzo(a)pyrene
Benzo(b) f luorsnthene
Benzo(k) f luoranthene
Benzo(g,h,l)perylene
Beryllium, total
alpha-BHC
beta-BHC
gamma-BHC (Llndane)
Bls-2-chloroethylether
Bis(2-ethylhexyl)
phthalate
Bromodichloromethane
Bronoform
2-Butanone (MEK)
Cadmium, total
Carbofuran
Carbon dlsulflde
Carbon tetrachloride
Chlorobenzene
Chlordane
Chloride
Chloroform
2-Chloronaphthalene
2-Chlorophenol
3-Chlorophenol
4-Chlorophenol
Chromium (total)
Chromium (hexavalent)
Chromium (trivalent)
Chrysene
Color
Copper, total
Corrosivity
Cyanide
Limits
(a)
10
10
100
5
-
5
-
-
0.05
-
10
30
10
-
20
2
-
10
10
10
10
10
2
0.05
0.05
0.05
10
10
1
2
10
1
-
5
1
2
0.1
-
0.5
10
5
-
-
10
-
-
10
-
60
-
40
MCI MCLG
(b) (c)
-
-
_
-*
-
-* -
-* -
-
sot
-
-
50*
-* -
1000*
5 0
-
-
-
-
-
-
-
-
- -
4*
-
-
100(1)
100(1)
-
10*
-*
-
5* 0
lot
-*
250,000t
100 (i)
-
-
-
-
50*
-
-
-
15 unitst -
l,000*t
noncorroslvet -
-
Proposed
MCLG (J)
_
-
-
0
-
0
9
-
-
-
-
50
7.0(10
1500
-
-
-
-
-
-
-
-
-
-
0.2
-
-
-
-
-
5
36
-
-
60
0
-
-
-
--
-
-
120
-
-
-
-
1300
-
-
Verified
Concentration
Risk Level
(e,f)
_
-
-
-
-
0.06
-
-
-
-
-
-
-
-
-
1
0.0002
-
-
-
-
-
-
-
-
0.03
SO
-
-
-
-
-
-
0.3
-
0.027
-
-
-
-
-
-
-
-
-
-
-
-
-
by IRIS
Concentration
at
RfD Level
(e.f)
_
-
3500
-
-
-
350
45.5
1.05
-
-
14
-
-
1750
-
-
-
-
-
-
-
175
-
-
10.5
-
700
700
700
1,750
-
175
3,500.
24.5
-
1.75
-
350
-
-
-
-
-
175
35,000
-
-
-
700
146
21,000
10
488
50
179,000
1,000
200
0.063
0.0012
0.42
0.022
0.19
0.058
0.000074
10
488
4
0.00046
0.19
50
170,000
200
3,433,000
0.65
0.000079
_
0.025
0.030(10
-
0.67
0.00015
j
3
'j
0.0039
0.013
0.023
0.017
-
_
-
146
-
.
1,000
_
-
-
-
_
-
-
-
.
-
-
15,000
0.19
-
0.0022
0.030 (k)
-
0.66
0.00012
1
j
J
3
j
0.0068
0.0092
0.0163
0.0186
0.03
_
-
45000
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
50,000
15.7
-
0.0175
-
-
40
0.00053
1
j
1
i
1
0.117
0.031
0.0547
0.0625
1.36
_
-
6.94
0.00048
15.7
10
1500
170
5
36
300
120
154
Word-searchable Version Not a true copy
E-2
-------
Table E-l
(Continued)
Hater Quality Criteria for Protection of toman IteaUhtg)
Chemical
ODD
DOE
DDT
2,4-D
DBCP
Dlbenxo (a ,h) anthrancene
Dlbutylphtnalate
1 ,2-Dlcnlorobenzene (o)
l,3-Dichlorobenzene(m)
l,4-Dlchlorobenzene(p)
1 ,2-Dlchloroethane
1 ,1-Dichloroethene
cls-l,2-Dlchloroethene
trans-1 , 2-Dichloroetbene
Dlchloromethane
1 ,2-Dlchloropropane
Dlchloropropene
Dleldrln
Dlethyl ph thai ate
Dimethyl ph thai ate
3-3 ' -Dlchlorobenzidln*
2 ,3-Dlchlorophenol
2 ,4-Dichlorophenol
2 , 5-Dlch lorophenol
2 ,6-Dlchlorophenol
3 ,4-Dlchlorophenol
2 ,4-Dlnethylphenol
2 ,4-Dlnltrotoluene
Dioxane
1 ,2-Dlphenylhydrazlne
Endosulfan
Endosulfan sulfate
Endrln
Epichlorohydrin
Ethylbenzene
Ethylenedlbromlde
Ethyleneglycol
Fluoranthene
Fluorene
Fluoride
Foaming agents
Halomethanes
Heptachlor
Heptachlor epoxide
Hexachlorobenzene
Hexachlorobutadlene
Hexachlorocyclopentadlene
Hexachloroethane
Hexane
Indenotl,2,3-cd)pyrene
Iron, total
Isophorone
Lead, total
Mangen«se, total
Mercury (alkyl)
Mercury (Inorganic)
Bethoxychlor
Practical
Quanti-
fication
Limits
(a)
0.1
0.05
0.1
10
5
10
2
2
5
2
0.5
1
..
1
5
0.5
5
0.5
5
5
20
-
5
-
10
-
5
0.2
150
0.1
0.5
0.1
2
5
-
10
10
-
-
1
0.05
1
0.5
5
5
0.5
-
10
10
10
-
2
-
2
MO,
(b)
.
-
-
100*
-
-
-
-*/10t
-/5t
75/5t
5
7
-*
.*
.
-*
-
-
-
-
-
-
-
-
-
-
-
-
-.
-
0.2
-.*
-*/30t
-*
-
-
-
2,000t
soot
0.10
_*
_*
-
-
-
-
-
300t
-
50
50t
-
2*
100*
HOG
(c)
_
-
-
-
-
-
-
-
-
75
0
7
.
-
.
-
-
-
-
-
-
-
-
-
-
-
-
-
.
-
.
-
-
-
-
-
-
-
.
-
-
-
-
-
-
-
-
-
-
Proposed
MCLG(d)
_
-
-
70
0
-
-
-
-
-
-
-
70
70
-
6
»
-
-
-
-
-
-
-
-
-
-
-
..
-
0
680
0
-
-
-
-
-
-
0
0
-
-
-
-
-
-
-
20
-
-
3
340
Verified
Concentration
at 10 °
Risk Level
(e,f)
_
-
-
0.01
-
-
-
-
-
0.4
0.06
-
-
5
-
-
-
-
-
-
-
-
-
-
-
-
-
0.05
-
-
3
-
-
-
-
-
-
-
0.008
0.004
0.5
-
3
-
-
-
-
-
-
-
m Must Be
by IRIS
Concentration
at
RfD Level
(e,f)
.
-
17.5
350
-
-
3,500
-
-
-
-
315
-
-
2,100
-
10.5
-
28,000
-
-
-
105
-
-
-
-
-
-
1.75
-
-
70
3,500
-
70,000
-
-
-
-
17.5
0.455
70
245
35
-
-
-
-
-
-
-
-
Ingestlon of
Drinking Water
Only
Threshold
Toxlcity
Protection
_
-
-
-
-
-
44,000
470
470
470
-
-
-
-
-
-
87
-
-
350,000
-
-
3,090
-
-
-
-
-
-
138
-
1
2,400
-
-
188
-
-
-
-
-
-
206
-
-
-
-
5,200
5O
-
-
10
ID'6
Cancer
Risk
,.
-
0.0012
-
-
j
-
-
-
0.033
-
-
0.19
-
0.0011
-1
-
-
-
-
-
-
-
-
0.11
-
0.046
-
-
-
.
-
-
-
-
-
-
0.19
0.011
0.021
0.45
-
-
-
-
-
-
-
-
Ingestlon of Drinking
Hater and Aquatic
Organisms
Threshold
Toxlcity
Protection
-
-
-
-
-
34,000
400
400
400
-
-
-
-
-
-
87
-
350,000
313,000
-
-
3,090
-
-
-
-
-
-
-
74
-
1
1,400
**
42
-
-
-
~
-
-
206
1.9
-
-
-
5,200
50
50
**
0.144
100
10-«
Cancer
Risk
..
-
0.000024
100
-
J
-
-
-
0.94
0.033
-
-
0.19
-
-
0.000071
-
-
0.01
-
-
-
-
-
-
0.11
-
0.042
-
-
-
:
~
~
-
-
-
*
0.19
0.00028
0.00028
0.00072
0.45
-
~
-
~
*"
*
*
"
Ingestlon of
Aquatic Organ is«a
Only
Threshold
Toxlcity
Protection
_
-
-
-
-
-
154,000
2,600
2,600
2,600
-
-
-
-
-
-
14,000
-
1,800,000
2,900,000
-
-
3,090
-
-
-
~
-
-
159
-
-
3,280
-
54
-
-
-
"
':
-
14,800
*"
-
~
"
520,000
-
100
0.146
ODH
Health
, Advisory (h)
10~° Lifetime
Cancer
Risk
_
-
0.000024
-
-
j
-
-
-
-
243
1.85
-
-
15.7
-
-
0.000076
'-
-
0.02
-
-
-
-
-
9.1
-
0.56
-
-
-
-
"
**
~
~
-
-
15.7
0.00029
0.00029
0.00074
50
*
8.74
*"
*
""
"
**
~
"
70 kg
Adult
_
-
-
70
-
-
-
620
620
75
-
7
70
70
-
-
-
-
-
-:
-
-
-
-
~
-
~
-
-
0.32
680
"
7000
*
"*
~
""
_
~
"
"*
"
*"
17
. i
340
Word-searchable Version Not a true copy
E-3
-------
Table E-l
(Continued)
Hater Quality Criteria for .Protection.of Human Health(g)
2-Methy1-4-chlorophenol
3-Methy1-4-chlorophenol
3-Met!tyl-6-chloropoenol
4-Methyl-2-pentanone (MIBK)
4-Methylphenol
Nlcfcel, total
Nitrate-N
Nltrite-N
Nitric oxide
Nitrobenzene
n-Nitrosodliwthylauioe
n-Nitrosodiethylanine
n-Nitrosodi-n-butylanine
n-Nitrosopyrrolidine
n-Nltrosodlpbenylaaine
Odor
OxaBic acid
PCB's
PAHs
Pentacblorobenzene
Pentachlorophenol
PH
Pbenanthrene
Phenol
Pyrene
Radiuo-226 and 228
Selenium, total
Silver, total
Styrene
Sulfate
2,3,7,8-TCDO
Tetrachloroetbene
1,1,1,2-Tetrachloroethane
2,3,4,6-Tetrachlorophenol
Thalliua, total
Toluene
Total dissolved solids
Toxaphene
2,4,5-TP
1,2,4-Trichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trlchloroethene
2,4,5-Trichloropbenol
2,4,6-Trichlorophenol
Vanadium
Vinyl chloride
Xylene
Zinc, total
5
10
50
-
-
10
10
10
10
10
10
50
10
5
-
10
1
10
20
70
1
-
0.005
0.5
0.5
10
10
2
-
2
2
10
5
0.2
1
10
5
40
2
5
20
-
*
-
10,000
-
.
-
-
-
-
~
3 unitst
-*
..
-*/30i
6.5-8.5
-
-
..
5(n)tt
10*
50*/90t
lOt
250,000t
-
-*
-
-
«
-*/40t
500,000t
5*
-*
-
200
-
5
-
-
-
2
-*/20t
5,000
-
-
-
10,00
1,00
-
-
-
-
-
-
-
_
-
-
-
-
-
-
-
«
-
-
-
-
-
-
~
.
-
-
-
-"
200
-
0
-
-
-
0
-
-
0.006
0.02
7
0
220
45
140
2,000
0
0.175
0.6
3
1.75
0.015
1,750
700
35,000
3,SCO
3,500
17.5
440
28
1,050
1,400
105
7,000
350
1,050
10,500
700
3,150
7,000
3,500
315(1)
350
7,350
Ingest ion
of
Drinking Hater
Only
Threshold
Ingestlon ot DrinXing
Hater and
Aquatic
Organisms
ID'6
Toxlcity Cancer
Protection
15.4
-
-
19,800
-
-
-
-
-
-
-
.
1,010
3,500
10
50
_
_
-
-
17.8
15,000
_
-
19,000
-
_
-
..
RisK
. -
-
-
-
0.0014
0.0008
0.0064
0.016
7.0
0.013
0.0031
_
_
-
~
-
1.8e-7
0.88
0.17
-
_
-
0.026
_
0.60
2.8
-
1.8
2
Threshold
Toxlcity
Protection
13.4
-
-
19,800
-
-
-
;
:
-
74
1,010
3,500
10
50
-
_
_
-
-
13
14,300
..
-
18,400
-
-
2,600
-
_
ID"6
Cancer
RlsX
-
-
-
_
0.0014
0.0008
0.0064
0.016
4.9
0.000079
0.0028
-
-
-
_
-
-
1.3e-8
0.80
0.17
1
-
-
0.00071
10
.
0.6
2.7
-
1.2
2.0
Ingestion of
Aquatic
OrqaiUsns
Only
Threshold
Toxicity
Protection
100
-
-
.
-
-
-
-
w
-
85
_
-
I
-
-
_
-
-
-
48
424,000
-
-
1,030,000
-
-
-
-
-
lO'6
Cancer
Risk
-
-
-
-
16
1.2
0.587
91.9
16.1
0.000079
0.031
-
-
-
_
-
-
1.4e-8
8.85
10.7
-
-
-
0.00073
-
-
41.8
80.7
-
3.6
525
QDW
Health
Advisory(h)
Li£etl»e
70 Kg
Adult
150
10,000
1,000
_
-
-
-
_
_
-
-
220
:
_
-
140
_
10
-
-
-
2,420
-
52
2OO
-
-
-
-
5,000
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E-4
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Table E-l
(Continued)
a. Source: 52 FR 25947. Practical quantification limits presented are for standard analytical methods. It way be appropriate to use different analytical methods to achieve lower quantification
limits in some cases.
b. 40 CFR 141 and 143.
c. 40 CFR 141.50.
d. 50 FR 46936; November 13, 1985.
e. Integrated Risk Information System database.
f. Assuming drinking water ingestion of 2 liter/dary and body weight of 70 kq.
g. 45 FR 79318-79379; November 28, 1980.
h. U.S. EPA, He^^^^^^LSp^^s, March 1987.
i. Based on the standard for Total tribalomethanes of 100 ug/1.
j . Based an criteria for polycyclic aromatic hydrocarbons (PAHs).
k. Million fibers/liter.
1. For vanadium pentoxide.
m. See also U.S. EPA "Comparisons of Office of Drinking Water and Office of Water Regulations and Standards for 307 (A) Toxic Pollutants" for updated volumes of priority pollutants.
* MCL will be proposed in the Federal Register in 1988. MCLs will also be proposed for aldicarb sulfoxide, aldicarb sulfone, atrazine, and dibromochloropropane.
t Secondary MCL.
tt n = pCi/1.
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Table ES2
U.S. EPA WATER QUALITY CRITERIA FOR PROTECTION OF AQUATIC LIFE
As of September 2, 1986
(ug/1)
Concentration
Acenapthene
Acrolein
Acrylonitrile
Aldrin
Alkalinity
Ammonia
Antimony
Arsenic (pentavalent)
Arsenic (trivalent)
Bacteria
Benzene
Benzidine
Beryllium
BHC
Cadmium
Carbon tetrachloride
Chlordane
Chlorinated benzenes
Chlorinated naphthalenes
Chlorine
Chloroalkyl ethers
Chloroform
2-Chlorophenol
4-Chlorophenol
4-Chloro-3-methyl phenol
Chromium (hexavalent)
Chromium (trivalent)
Copper
Cyanide
DDT
Freshwater
Acute
Criteria
1,
7,
9,
5,
2,
35,
1,
238,
28,
4,
1,
700b
68b
550b
3.0
S
CRITERIA ARE
000b
850b
360
FOR PRIMARY
300b
500b
130b
100b
3.9a
200b
2.4
250b
600b
19
000b
900b
380b
S
30b
16
700=
18 =
22
1.1
Freshwater Marine
Chronic Acute
Criteria Criteria
520b
21b
2,600b
S
20,000
pH AND TEMPERATURE DEPENDENT
1, 600b
48b 2,
190
RECREATION AND SHELLFISH USES
S 5,
S
5.3b
S 0
l.la
S 50,
0.0043
50b
S
11
S
1,240"
2,000b
S 29,
S
970b
55b
S
1.3
S
S
319b
69
100b
S
S
.34b
43
000b
0.09
160b
S
13
S
S
S
700b
S
11 1,100
210= 10,
12 =
5.2
0.001
300b
2.9
1
0.13
Marine
Chronic
Criteria
710b
S
S
S
S
S
13b
36
700b
S
S
S
9.3
S
0.004
129b
7.5b S
7.5
S
S
S
S
S
50
S
2.9
1
0.001
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E-6
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DDE
TDE
Derneton
Dichlorobenzenes
1,2-Dichlorethane
Dichloroethylenes
2,4-Dichlorophenol
Di chloropropane
Dichloropropene
Dieldrin
2,4-Dimethyl phenol
Dinitrotoluene
2,3,7,8-TCDD
1,2-Diphenylhydrazine
Endosulfan
Endrin
Ethylbenzene
Fluoranthene
Guthion
Haloethers
Halomethanes
Heptachlor
Hexachloroethane
Hexachlorobutadi ene
Lindane
Hexachlorocyclopentadiene
Iron
Isophorone
Lead
Malathion
Mercury
Table E-2
(Continued)
Concentration
Freshwater
Acute
Criteria
l,050b
0.06b
S
l,120b
118,000b
ll,600b
2,020b
23,000b
6,060b
2.5
2,120b
330b
<0.01b
270b
0.22
0.18
32,000b
3,980b
S
360b
ll,000b
0.52
980b
90b
2.0
7b
S
117,000b
82a
S
2.4
Freshwater
Chronic
Criteria
S
S
0.1
763b
20,000b
S
365b
5,700b
244b
0.0019
S
230b
<0.00001b
S
0.056
0.0023
S
S
0.01
122b
S
0.0038
540b
9.3b
0.08
5.2b
1,000
S
3.2a
0.01
0.012
Marine
Acute
Criteria
14b
3.6b
S
l,970b
113,000b
224,000b
S
10,300b
790b
0.71
S
590b
S
S
0.034
0.037
430b
40b
S
S
12,000b
0.053
940b
32b
0.16
7b
S
12,900b
140
S
2.1
Marine
Chronic
Criteria
S
S
0.
S
S
S
S
3,040b
S
0.
S
370b
S
S
0.
0.
S
16b
0.
S
6,400b
0.
S
S
S
S
S
S
5.
0.
0.
1
0019
0087
0023
01
0036
6
01
025
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E-7
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Methoxychlor
Mi rex
Naphthalene
Nickel
Nitrobenzene
Nitrophenols
Nitrosamines
Parathion
PCBs
Pentachlorinated ethanes
Pentachlorophenol
Phenol
Phthalate esters
Polynuclear aromatic hydrocarbons
Selenium
Silver
Sulfide
Tetrachlorinated ethanes
1,1,2,2-Tetrachloroethane
Tetrachloroethanes
Tetrachloroethylene
2,3,5,6-Tetrachlorophenol
Thallium
Toluene
Toxaphene
Trichlorinated ethanes
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichloroethylene
Freshwater
Acute
Criteria
S
S
2,300b
1,80O
27,000b
230b
5,850b
S
2.0
7,240b
55b
10,200b
940b
S
260
4.1a
S
9,320b
S
9,320b
5,280b
S
l,400b
17,500b
1.6
18,000b
S
S
45,000b
Table E-2
(Continued)
Freshwater
Chronic
Criteria
0.03
0.001
620b
96a
S
150b
S
0.04
0.014
l,100b
3.2b
2,560b
3b
S
35
0.12
2
S
2,400b
840b
S
40b
0.013
S
S
9,400b
21,900b
Concentration
Marine
Acute
Criteria
S
S
2,350b
140
6, 680b
4,850b
3,300,000b
S
10
390b
53b
800
2,944
300b
410
2.3
S
S
9,020b
10,200b
S
2,130b
6,300b
0.07
S
31,200b
S
2,000b
Marine
Chronic
Criteria
0.03
0.001
S
7.1
S
S
S
0.04
0.03
281b
34b
S
3.4b
S
54
-
2
S
S
450b
440b
S
5,000b
S
S
S
S
S
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E-8
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Table E-2
(Continued)
Concentration
Freshwater
Acute
Criteria
2,4,6-Trichlorophenol
Zinc
Freshwater
Chronic
Criteria
970b
47
Marine
Acute
Criteria
Marine
Chronic
Criteria
170
58
aHardness dependent criterion (100 mg/1 used).
blnsufficient data to develop criteria. Value presented is the L.O.E.L.--lowest observed effect level.
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E-9
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Appendix F
Sample Letter to Obtain Property Access
[date]
PRP Name
Street Address
City
Re: Superfund Site
Dear :
As you may know, the U.S. Environmental Protection Agency (EPA) is conducting a Remedial
Investigation/Feasibility Study in the [Site name] area to determine both the sources and
extent of [ground water/soil/air] contamination. This contamination has resulted from the
improper disposal of [chemicals] that pose a threat to the public health and the environment.
The EPA is scheduling [soil/soil gas/air/ground water, etc.] sampling activities on
properties in your area. The sampling is designed to determine if contamination is present in
[shallow soils/surface water/ground water/the air]. This sampling activity is scheduled to
occur sometime during the week(s)of [date]. EPA's current plans call for [a type of sampling,
e.g., soil borings; installing a ground water monitoring well for subseguent sampling; air
sampling] to take place on your property at [address] on [day/week/during this time] (or) EPA
will need to secure access to a portion of your property for approximately [weeks/months] to
complete construction of a [well/facility].
Your cooperation is reguested in giving EPA representatives access to your property to
complete this sampling/construction activity. In order for us to plan successfully, we would
appreciate your signing this letter below and returning it in the envelope provided. You may
wish to keep a copy for your records. When the sampling program is completed the EPA will
furnish you with the test results of samples taken on your property.
The sampling will consist of [specify details of activity]. The [soil/soil gas/surface
water/ground water/air] sampling on your property should not take more than [hours/days].
Our work there may involve some disturbance of the [soil/pavement/vegetation/sprinkler systems]
on you property [including drilling small holes/digging a temporary trench, etc.]. We will take
care to restore your property to substantially the same condition that existed prior to the
work. All holes will be filled and regraded.
[Optional paragraphs 1-7 (may be used in follow-up letter)]:
We understand that you have some concerns about EPA entering your property and conducting
the above activities. You may be concerned about:
[1] liability for damages, injuries, and indemnification;
[2] danger to your health;
[3] the level and guality of restoration to your property;
[4] split samples to be provided by EPA;
[5] the availability of test results for the site;
[6] the legal conseguences of denying access to EPA;
[7] special considerations that you have reguested.
The EPA is taking the above action because of its responsibility to respond to contaminated
sites under the Comprehensive Environmental Response, Compensation and Liability
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F-1
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Act (Superfund), 42 U.S.C. Section 9601. If you have any questions, please call me at (415)
974-xxxx, or contact [name] of our Office of Regional Counsel at (415) 974-xxxx. Thank you for
your cooperation.
Sincerely,
[Name]
Remedial Project Manager
Enclosure
PLEASE SIGN BELOW AND RETURN THIS LETTER IN THE ENCLOSED ENVELOPE
My signature below acknowledges that I have read this letter and agree that EPA, their
representatives or contractors, may enter my property during the week of [date] to conduct the
activities specified above.
Signature Date
Address
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F-2
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OPTIONAL PARAGRAPHS
[1] I understand that you have expressed some concerns about indemnification for personal
injury or property damage as a result of EPA conducting the above activities on your property.
You should be aware that the EPA does not enter into indemnification agreements with
landowners. However, EPA does have a written agreement with , our contractor,
reguiring it to carry a comprehensive insurance policy to cover claims for personal injury,
death, or property damage to third parties. In addition, should the claim exceed the policy
limit, set at a minimum of [$(1,000,000)] per occurrence, the EPA has agreed to pay for any
excess liability. If this does not provide adeguate compensation, the only direct remedy
against the EPA is to file a claim under the Federal Tort Claims Act, 28 U.S.C. Sections
2671-2680.
[2] I understand that you have expressed concern about this site presenting a health threat.
At this time, EPA is not aware of any immediate health threat posed to you from this site. In
addition, EPA has taken precautions to minimize any potential health threat to both the on-site
workers and off-site residents during field activities. A Health and Safety Plan, a document
available to the public, has been developed for this site to insure that adeguate monitoring is
conducted to determine the level of protective clothing reguired for on-site workers and any
potential exposures to off-site residents. You will be notified if contaminants are detected at
the site boundaries above safe levels. The site will be secured to minimize exposure to non-EPA
personnel. Therefore, EPA field activities are not expected to pose a health threat to any of
the residents in your area.
[3] I understand that you have expressed concern regarding the level and guality of
restoration of your property. During the course of EPA's field activities, there is the
possibility that your property may be disturbed. EPA will restore your property in the event of
this disruption. The restoration will be at the level of current construction practices and
will attempt to remedy any disruption. Examples of this restoration will be to fill and patch
any damaged concrete or asphalt and replant any landscaping. We would like to work with you
during our activities to minimize any disturbance to your property.
[4] I understand that you have expressed concern regarding the samples obtained from your
property. At your reguest, we will provide to you free of charge a portion of the
[air/water/soil] sample in an appropriate container. If you wish to compare the results from
your sample with EPA's results, you must follow the protocols listed in the [site name]
Quality Assurance/Quality Control Plan, a document that can be made available to the public.
These protocols include the specific type of laboratory testing and shipping procedures
reguired. If you wish to obtain a sample, please notify me at least 48 hours before the field
work begins.
[5] I understand that you have expressed concern regarding the availability of test results
from the site. The results of tests from your property will be sent to you as a matter of
course when these results have been received and verified by EPA. If you wish, you may obtain
the sample results from tests conducted at other locations within the [site name] upon reguest.
[6] You should be aware that the Superfund law specifically gives EPA a right to access
private property in Section 104 (e) (4) (A) . This section states that "any officer, employee, or
representative is authorized to inspect and obtain samples from any vessel, facility,
establishment, or other place or property or from any location of any suspected hazardous
substance or pollutant or contaminant." You may be subject to a civil penalty of up to $25,000
for each day that you fail to grant access to the EPA.
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U.S. GOVERNMENT PRINTING OFFICE: 1989-648-163/87077
F-3
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