United States Office of Emergency and EPA/540/G-88/003 

Environmental Protection Remedial Response OSWER Directive 9283.1-2 

Agency Washington DC 20460 December 1988 

Superfund 

Guidance on Remedial 

Actions for 

Contaminated Ground 

Water at Superfund 

Sites 

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EPA/540/G-88/003 

OSWER Directive 9283.1-2 

December 1988 

Guidance on Remedial Actions for 

Contaminated 

Ground Water at Superfund Sites

Interim Final 

Office of Emergency and Remedial Response 

U.S. Environmental Protection Agency 

Washington, DC 20460 

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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 

CERCLA--and 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 Rl/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 Integrated Risk Information System

ISV In situ vitrification

Koc Organic carbon partition coefficient

Kp 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/Sl 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

Caroline Roe/OERR

Betsy Shaw/OERR

Bill Hanson/OERR

Betti Van Epps/OERR

Joanne Bahura/OSW

Lisa Lefferts/OSW

Vern Myers/OSW

David Lang/Region I

Damian Duda/Region II

Kathy Davies/Region III

Gregg Kulma/Region V

Ruth lzraeli/Region VI

Jeff Rosenbloom/Region IX

Walter Walsh/OPA 

Craig Zamuda/OPA 

Steve Nicholas/OPA 

Jose Valdes/OGWP 

Candice Wingfield/OWPE 

Joe Freedman/OGC 

Jerry Jones/RSKEL 

Scott Huling/RSKEL 

Edward Barth/HWERL 

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 

(RI) 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 RI 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 Rl/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 Rl/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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Figure 1-2 Overview of the Ground-Water Remedy Selection Process. 

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Table 1-1. EPA Guidance Documents Pertinent to Ground-Water Remedial Actions Under Superfund* 

Issuing 

Title Office Citation Status Contents Possible Resource for 

Alternate Concentration OSWER EPA/530-SW-87-107 Final Describes how to Setting cleanup levels 

Limit Guidance develop alternate for exposure-based 

concentration limits scenarios for Class III 

under RCRA. ground water 

Compendium of Superfund OERR EPA/540/P-87-001a & b Final Presents techniques Scoping and field 

Field Operations Methods August 1987 used during the investigation during the 

fieldwork phase of the RI RI 

Data Quality Objectives for OERR/OWP EPA/540/G-87/003a Final Identifies the framework Scoping activities 

Remedial Response E and process by which 

Activities (DQO Guidance) DQOs are developed. 

DQOs are qualitative 

and quantitative 

statements specifying 

the quality of data 

needed to support 

Agency decisions. 

Endangerment Assessment OWPE U.S. EPA 

Handbook August 1985 Draft Provides guidance on RI 

conducting 

endangerment 

assessments. 

Exposure Factors ORD U.S. EPA Draft Guidance for assessing Selection of exposure 

Handbook September 1987 human exposure. assumptions and pathways 

for drinking water 

Ground-Water Protection OGWP U.S. EPA Final Provides framework for Scoping 

Strategy August 1984 protecting ground water. 

Guidance for Applicants OGWP U.S. EPA Final Explains EPA’s policies Determining response 

for State Wellhead June 1987 and procedures for objectives 

Protection Program implementing the 

Assistance Funds Under wellhead protection 

the Safe Drinking Water assistance program. 

Act 

OERR U.S. EPA Interim Provides an RI/FS process 

Guidance for Conducting March 1989 Final understanding of the 

Remedial Investigations and RI/FS process. 

Feasibility Studies under Presents structure for 

CERCLA conducting an RI/FS. 

OERR U.S. EPA Final Provides guidance or Taking removal actions, 

Guidance Document for October 1987 planning and formulating remedial 

Providing Alternate Water implementing programs alternatives 

Supplies to provide alternate 

water supplies. 

OERR U.S. EPA Draft Guidelines for Documentation of the 

Guidance on Preparing March 1988 documenting and selected remedy 

Superfund Decision amending Proposed 

Documents Plans and RODs. 

(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 

Issuing 

Title Office Citation Status Contents Possible Resource for 

Guideline for Delineating OGWP EPA/440/6-87-010 Final Describes procedures Determining response 

Wellhead Protection Area and information needed objectives 

to specify wellhead 

protection areas. 

Guidelines for Ground-Water OGWP U.S. EPA, Draft Presents methods used Classifying ground 

Classification Under the EPA April 1988 to classify aquifers. water 

Ground-Water Protection 

Strategy 

Handbook for Remedial OSW U.S. EPA, Final Provides basic Alternative 

Actions at Waste Disposal October 1985 understanding of development, screening, and 

Sites remedial actions, evaluation 

describes how to select 

remedial actions, and 

gives an example. 

Methods for Determining the NWWA/EPA NWWA, 1987 Final Presents methods for Field investigation 

Locations of Abandoned locating abandoned during the RI 

Wells wells. 

Modeling Remedial Actions OERR/ORD EPA/540/2-85-001 Final Presents model FS 

at Uncontrolled Hazardous April 1985 selection and use 

Waste Sites guidelines for assessing 

site conditions and 

remedial action 

performance. 

RCRA Ground-Water OWPE U.S. EPA, OSWER Final Describes the essential Technical 

Monitoring Technical Directive 9950.1, components of a RCRA considerations during 

Enforcement Guidance September 1986 ground-water scoping and 

Document monitoring system. performance evaluation 

Superfund Exposure OERR U.S. EPA, OSWER Final Provides overall RI (and modeling) 

Assessment Manual Directive 9285.5-1, understanding of the 

March 22, 1988 integrated exposure 

assessment process, 

references estimation 

procedures and 

computer modeling 

techniques. 

Superfund Public Health OERR EPA/540/1-86/060 Final Provides guidance on RI, selecting indicator 

Evaluation Manual (OSWER Directive methods for evaluating chemicals, and 

9285.1-1), October effects to human health. determining aggregate 

1986 effects 

The CERCLA Compliance OERR EPA, June 1987, Interim Identifies potential Scoping, FS 

With Other Laws Manual OSWER Directive Final ARARS, procedures for 

9243.1-01 identifying ARARs, 

waiver criteria, and 

hypothetical scenarios. 

Water Quality Standards OW/Regula- U.S. EPA, Final Guidance and Determination of 

Handbook tions and December 1983 implementation of preliminary cleanup 

Standards WQC. 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 (NCP) (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 Conservation and Recovery Act 

(RCRA) 

! 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 

121(b)) 

! 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)). 

! 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 

preliminary cleanup levels. 

! 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 activitybased 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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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 groundwater 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 (IIB) for 

drinking water, agriculture, or other beneficial use. 

Ground water not considered a potential source of drinking 

water and of limited beneficial use (Class IIIA and Class IIIB) 

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 IIIA includes ground water that is interconnected to 

surface water or adjacent ground water that potentially could 

be used for drinking water. Class IIIB includes ground water 

that has no interconnection to surface water or adjacent 

aquifers. For Class IIIA 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 Ill. 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 of RCRA to GroundWater 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 POTW's 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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Table 2-1. Schedule for Implementation of the Land Disposal Restrictions 

Effective Date of Ban Wastes 

Solvents and Dioxin 

Wastesa 

California List Wastesb 

Remaining Wastesc 

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 nonCERCLA/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 BDAT is 

solids incineration 

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 

November 8, 1984 

November 8, 1986 

November 8, 1988 

November 8, 1990 

November 8, 1988 

November 8, 1988 

November 8, 1988 

November 8, 1988 

July 8, 1987

July 8, 1987

November 8, 1988

July 8, 1989

November 8, 1990

August 8, 1988 

August 8, 1990 

August 8, 1990 

August 8, 1990 

August 8, 1990 

August 8, 1990 

June 8, 1989 

May 8, 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 bThe 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 groundwater 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 point–-the 

boundary of the waste management area–-if 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. 

3.2.1 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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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 sitespecific 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: 

Volatiles Non-volatiles 

Carcinogens Lower of (50% x Lower of DWEL 

DWEL) and and 10-4 excess 

10-4 excess lifetime cancer 

lifetime cancer risk 

risk 

Noncarcinogens 50% x DWEL 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 for a 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 sitespecific 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 μg/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--Is 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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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 water from 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 RI 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 RI 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 12A was one of 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 

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 

RI 

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) 

! Evaluation of plume movement and response 

! Assessment of design parameters for potential 

treatment technologies 

! Consideration of technical uncertainty 

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Figure 3-3 Exposure Pathway Related to Ground Water. 

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Table 3-1. Questions to Focus Data Collection Activities 

-

-Will contaminants continue to migrate from the source to the ground water at levels that exceed 

health-based or environment-based standards? 

Level of Contamination -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? 

Exposure to Class I or IIA

Contamination 

on the Basis of

Ground-Water

Classification

Class IIB 

Class III 

-Which ground-water classification describes the ground water?

-Is any domestic well water contaminated above health-based levels?

-Is an alternative water supply in use?

-Is the ground water ecologically vital?

-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? 

-Could the contamination migrate and contaminate Classes I, IIA, or IIB ground water or surface 

water? 

Single Nonaqueous Phase 

Contaminant Single Aqueous Properties Phase Affecting 

Treatment 

Mixed Phases 

-Is the flashpoint of the non-aqueous phase below 80 degrees F?

-Is metal removal required?

-Can the non-aqueous liquid be recycled?

-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? 

-Will pumping result in an emulsion? 

Natural 

Attenuation 

Response

Action 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 spread of contaminants above 

health-based or environment-based levels beyond current boundaries? 

-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 & -Is the aquifer amenable to extraction, considering transmissivity, interconnection, etc? 

Action Discharge 

(continued) -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? 

Biodegradation -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 longterm 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 groundwater 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 groundwater 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, semivolatiles, 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 sitespecific 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, 

Fg/g, to the concentration of contaminant in ground water, 

Fg/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 RI 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 RI. 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 RI 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 no onsite 

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 f OC 

where 

Kd = soil/water partition coefficient 

KOC = organic carbon partition coefficient 

fOC = 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: 

where: 

C = concentration 

M 

t = = mass of contaminant introduced at the point sourcetime 

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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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 That 

Incorporated in Models (1) Qualitatively (2) 

Processes and Variables Frequently Should Be Considered 

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 Parametersa 

Extraction 

Air-stripping 

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 

Aquifer storage coefficient

Soil type/porosity

Hydraulic conductivity

Aquifer saturated thickness

Contaminant sorpton

Contaminant solubility

Contaminant volatility

Disposal of treated water

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

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

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 in Chapter 6, should be made. Data to reduce the uncertainty 

example of a sensitivity analysis. of important variables should be collected throughout the 

remedial selection, design, and construction phases to refine 

If there is sufficient confidence that a particular remedy will be and modify the remedy. 

effective for a site, a detailed evaluation, which is discussed 

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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 RI 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 10-4 to 10-7 unit 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 computerbased 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--If 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. (May be 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, 1987i). 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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Figure 4-1 Flow Chart for Determing Site-Specific Cleanup Levels on the Basis of Existing Standards and 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 q1*, 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: 

RSD (mg/kg day) x body weight (kg) 

Conc. (Mg/l)= drinking water injestion rate (l/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- observedadverse-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: 

RfD (mg/kg day) body weight (kg) 

DWEL (mg/l) = drinking water ingestion rate (l/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 

ln 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 

10-4 to 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: 

where i = chemical i in the mixture, and DIi = 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 10-5

 was 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 1,1,2-Trichloroethane 

Methylene chloride 1, 1-Dichloroethene 

Chloroform Trichloroethene 

Tetrachloroethane 1,4-Dioxane 

1,2-Dichloroethane 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 Timing of exposure 

to 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 Effectiveness and 

to Uncertainty 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/quantification limits for 

contaminants 

If standard laboratory procedures can only detect contaminants at concentrations reflecting the 

10-4 risk level, 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.) 

Technical 

limitations to 

restoration 

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. 

Background levels 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 near surface 

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 

withdrawsup to 18 mgd from the Licking River and serves about 75,000 people. The site was used by the city for the disposal 

of residential and commercial 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 

Ground-Water 

Concentration, 

mg/l 

Proposed 

ACL, mg/l1 

Standard or 

Health-Based 

Criteria, 

mg/l 

Projected 

Concentration 

in the 

Licking River, 

mg/l 

Arsenic 0.064 0.64 0.05 (MCL) 1.6 x 10-6 

Barium 7.4 74 1 (MCL) 1.9 x 10-4 

Chromium 1.5 15 0.05 (MCL) 3.8 x 10-3 

Nickel 2.4 24 0.13 (WQC) 6.0 x 10-5 

Toluene 0.017 0.17 0.14 (WQC) 4.2 x 10-3 

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 RI to assist in planning cost-effective RI 

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. 

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 contaminants--this 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. 

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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 RI; 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 

! 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 IIB), 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 available for the 

contaminants in the ground water 

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 biorestoration 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 for a 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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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--In 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 groundwater remedial action. Alternatives are developed from 

combinations of these various process options. 

Examples of remedial alternatives include the following: 

! Active restoration--Three extraction wells pumping at a 

rate of 10 gpm to a carbon adsorption unit and 

discharging to a POTW 

! Plume containment--Installation of a bentonite barrier 

wall and use of well construction permits to prevent new 

well installation within the area of the plume 

! Natural attenuation--Monitoring 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 ARARs or other health-based levels, 

and protecting human health and the environment 

! Implementability with respect to technical and 

administrative feasibility of the alternatives and the 

availability of needed technologies and services 

! A general cost 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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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 groundwater 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: 

! Cost--Fund balancing is only appropriate if the relative 

level of the cost is high. 

! Availability of Superfund Monies to Respond to Other 

Sites--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 RI 

! 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: 

2 Expected pumping and/or flow rates 

2 Number of extraction wells 

2 Treatment process 

2 Control of cross-media impacts 

2 Management of residuals 

2 Gradient control system description 

2 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 cleanup 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: minor changes, 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 document file 

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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Figure 7-1 Predicting Remedial Action Performance from Monitoring Data. 

of Significant Differences provided for under CERCLA Section information that prompted the change. Significant changes 

117(c). This document describes the differences and what involve a component of the remedy, such as a change in the 

prompted them and is announced in a newspaper notice. This volume of contaminated ground water that must be addressed, 

is placed in the administrative record for the site, along with or a switch from air stripping to carbon adsorption in a groundthe water pump and 

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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 groundwater 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., Applied Hydrogeology, 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, 1987i. 

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, 1987I. 

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 

Range of 

Concentrations 

Chemical Reporteda (Fg/I) 

Volatile Organic Compounds 

Benzene 20 - 120 

Bromadichloromethane 5 - 56 

Carbon disulfide 10 - 67 

Chloroethane 15 - 1,000 

1,1-Dichloroethene 50 - 1,900 

Trans-1,2-dichloroethene 37 - 1,000 

Methylene chloride 10 - 80 

Phenol 20 - 1,500 

Tetrachloroethene 45 - 650 

1,1,1-Trichloroethane 12 - 1,500 

Trichloroethene 6 - 1,200 

Vinyl chloride 45 - 500 

Phthalates 

Bis(2-ethylhexyl)phthalate 10 - 90 

Di-n-butyl phthalate 8 - 45 

Inorganics 

Aluminum 440 - 600 

Barium 99 - 200 

Calcium 10,300 - 20,750 

Copper 20 - 80 

Iron 999 - 1,500 

Lead 5 - 7 

Magnesium 4,000 - 7,000 

Manganese 70 - 80 

Nickel 2 - 5 

Potassium 1,500 - 2,000 

Sodium 6,550 - 10,000 

Zinc 32 - 50 

aExcludes samples in which the contaminant was not 

detected. 

detected above health-based levels in the shallow ground 

water; therefore, it has been classified Class IIB, 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 RI 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 RI, 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 RI 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 (10-7 

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 

Tank Removal, Vapor Extraction System, and 

Criterion Ground-Water Extraction Sealing Abandoned Well 

Protects Human Health and the Yes, reduces spread of contaminants to potential 

Environment exposure points. 

Meets ARARs Meets ARARs for ground-water discharge; does not 

meet ARARs in the aquifer (i.e.,health-based 

cleanup levels). 

Is Effective Over the Short-term 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. 

Is Effective Over the Long-Term Promotes long-term effectiveness by reducing 

contamination at the site. 

Reduces Toxicity, Mobility, or Reduces volume by removing and treating high 

Volume concentration zone 

Is implementable 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. 

Is Cost-Effective 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. 

Meets State’s Acceptance Yes, state approved. 

Meets Community’s Acceptance Yes, community strongly supports any action to 

remediate the site as early as possible, preventing 

contaminant migration. 

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. 

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 (K oc) 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 

A - 4 

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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 

POTW's 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 

! Cross-media effects are not anticipated 

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Table A-3

CONTAMINANT-SPECIFIC ARARs AND TBC REQUIREMENTS

HYPO-THETICAL SITE

All Values in ug/1

Water Quality Criteria 

Ingestion of 

Concentration Concentration Health Drinking Water Only 

State Corresponding Corresponding Advisories 

Maximum Maximum Contaminant Level Unacceptable to 10-6 to RfDs Lifetime 10-6 Excess 

Concentration Primary Secondary Proposed Pollutant Level for for Non- 70 kg Toxicity Cancer 

Chemical Reported (Health) (Welfare) MCLG MCLG Levels Carcinogensa Carcinogensa Adult Protection Risk 

Barium 200 1000 1500 1750 1500 

Benzene 120 5 0 1 0.67 

Bis(2-ethylhexyl) - 90 10 50 700 21000 

phthalate (DEHP) 

Bromodichloromethane 56 100 700 

Carbon disulfide 67 3500 

Copper 80 1000 1300 1000 

1,1-Dichloroethane (1,1-DCE) 1900 7 7 7 0.06 315 7 0.033 

t-1,2-Dichloroethane (1,2-DCE) 1000 70 70 

Di-n-butyl phthalate 45 3500 44000 

Iron 1500 300 

Lead 7 50 20 10 50 50 

Manganese 80 50 50 

Methylene chloride 80 5 5 2100 0.19 

Nickel 5 700 150 15.4 

Phenol 1500 1400 3500 

Tetrachloroethene (PCE) 650 50 0 25 350 10 0.88 

1,1,1-Trichloroethane (TCA) 1500 200 200 3150 200 19000 

Trichloroethene (TCE) 1200 5 0 3 2.8 

Vinyl chloride 500 2 0 0.015 2 

Zinc 50 5000 7350 5000 

aAssumes ingestion of 2 1/day and body weight of 70 kg. 

bIt is not required that all standards and criteria be identified; once an ARAR or TBC has been identified upon which a preliminary cleanup level can be based, identifying 

contaminant-specific ARARs and TBC requirements can stop. However, the aggregate effects levels generally should be determined for the site as they may affect selection and cleanup 

levels. 

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Chemical

Benzene

Bis-2-ethylhexylphalate

1,1-Dichloroethene

Methylene chloride

Phenol

Tetrachloroethene

1,1,1-Trichloroethane

Trichloroethene

Vinyl chloride

Sum 

Exposure Assumptions: 

Body weight = 70 kg 

Preliminary Cleanup

Level

(ug/1) 

5

10

7

5

1400 

25 

200 

5 

2 

Drinking water ingestion rate = 2 1/day

Exposure period = 70 years

Neg. = Negligible

Table A-4 

AGGREGATE RISK 

HYPO-THETICAL SITE 

Carcinogens 

Excess 

Lifetime 

Cancer Systemic Toxins 

Risk at DI/RfD at 

Preliminary Daily Preliminary 

Carcinogen Cleanup RfD Intake (DI) Cleanup 

Classification Level (mg/kgday) (mg/kgday) Level 

A 7x10-6 - - -

B2 2x10-7 0.02 0.001 0.05 

C 1x10-4 0.009 0.0002 0.02 

B2 1x10-6 0.06 Neg. Neg. 

- - 0.04 0.04 1.0 

B2 4x10-5 0.02 0.001 0.05 

- - 0.09 0.006 0.07 

B2 2x10-6 - - -

A 1x10-4 - - -

2x10-4 1.2 

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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 (DI) 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 Koc values are more mobile than contaminants with 

high Koc 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. 

! 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 RI, 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--10 ppb 

! PCE--50 ppb 

! 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 

Bromodichloromethane 

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 

Range of 

Concentrations 

Reported in 

Ground Watera 

(F/l) 

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 

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 

Cleanup Mobility 

Level Koc 

b 

(F/l) (mloc/g) 

5 83 

– – 

– 54 

– – 

0.7* 65 

350 59 

5 8.8 

1,120* 6.2 

25 364 

200 152 

5 126 

0.2* 57 

10 170000 

- -

-

- -

- -

- -

- -

- -

- -

- -

- -

- -

- -

- -

- ­

aSamples in which the contaminant was not reported are excluded. 

bThe organic carbon = mg contaminant/kg of organic carbon 

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--If 

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 

wells--This 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 Site--Industrial landfill, underground solvent 

storage tank 

Local Land Use--Residential 

Ground-Water Use--Upper aquifer--potential drinking water 

source; lower aquifer--current 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 Objectives--Prevent 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 Taken--Remove tank and surrounding 

soils; vapor extraction, and ground-water pumping; seal 

abandoned well 

ARARS--Nine 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 

Reduction of Mobility, 

Toxicity, or Volume 

Alternative (MTV) Implementability

Short-Term 

Effectiveness 

Long-Term 

Effectiveness 

Present 

Worth Cost 

Natural attenuation 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 

Pulsed pumping, 3 well Reduces risk to the 

points, air-stripping, community over the 

enhanced biodegradation short-term; potentially 

small exposure to 

workers; does not 

cause environmental 

impacts, restoration 

time frame is 12 

years. 

Pulsed pumping, 7 well Reduces risk to the 

points, air-stripping, community over the 

reinjection, enhanced short-term; potentially 

biodegradation 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 

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 

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 

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. 

$500,000 

$3,000,000 

$5,000,00 

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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 

WQC for Protection WQC for Protection 

of Human Health-- of Aquatic 

Drinking Water and Organisms--Fresh 

Chemical Fish Ingestion, ppb Water Organisms, ppb

Benzene

DEHP

Chloroform

Copper

Dichloroethenes

1,2-DCE

Iron

Manganese

Methylene chloride

PCE

1,1,1-TCA

TCE

Vinyl chloride

a = Acute effects

c = Chronic effects

0.66 

10,000 

0.19 

0.033 

0.94 

300 

50 

0.8 

18,400 

2.7 

2 

(C) 5300 (a) 

(S) 

(C) 1240 (c) 

12 (c) 

(C) 11600 (a) 

(C) 20000 (c) 

(S) 1000 (c) 

(S) 

(C) 

(C) 840 (c) 

(C) 

(C) 21900 (c) 

C = Carcinogenic effect (1x10-6 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 

B - 1 

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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 (TAC) that made decisions through consensus management. In addition to 

working on Superfund-related issues, the TAC 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 TAC 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 limited--the 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 groundwater 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/Sl) 

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 

B - 3 

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 sitespecific 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/Sl 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 

! 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 

Rl/FS is begun for any interim actions or operable units. To 

the extent possible, PRP-lead Rl/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 

B - 4 

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) 

B - 5 

! 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 ARARs--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 practicable--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. 

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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 ) = Cs(i - 1) - Cw(i -1) n 

(1) 

rb 

where: 

Cs(i) = the soil total volatile organics (TVO) 

concentration after i flushes, mg/kg 

Cw = the concentration of TVO in the water in 

equilibrium with the soil, mg/I 

n = the porosity of the soil 

b = the bulk density of the soil, mg/I 

Once the soil TVO concentration is calculated, the TVO 

concentration in the ground water is calculated by the 

following formula: 

Once equation (2) is evaluated, the value for Cw(i) can be 

entered into equation (1) as Cw(i-1) 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 

where: 

Kd = distribution coefficient 

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D-1 
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 = Ground-water VOC 

mass at time t mass at time(t-1) 

- Mass of VOCs pumped out 

+ Mass of VOCs leached 

into ground water from soil (3) 

where: 

Mw(t) = mass of VOC in ground water at t, kg 

Mw(t-l) = 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(t) = concentration of VOCs in ground water, kg/l 

T = time period of one iteration, which is set 

to 1 day 

M1(t:t-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. 

Figure D-1. Prediction of Ground-Water Restoration 

Time Frame Using the Batch Flushing Model 

Figure D-3. Prediction of Ground-Water 

Restoration Time Frame Using the Continuous 

Flushing Model 

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Appendix E 

Tables of U.S. EPA Water Standards, Criteria, and Guidelines for Establishing

Ground- Water Cleanup Levels 

E - 1 

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Table E-1 

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) 

This document provides a summary of information in the Superfund Public Health Evaluation Manual, the Integrated Risk Information System (IRIS) outputs, and other source documents. 

Only source documents should be referenced in the ROD. For additional information contact your regional coordinator or the Office of information Resources Management. 

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Table E-1 

(Continued) 

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Table E-1 

(Continued) 

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Table E-1 

(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, Health Advisories, March 1987.

i. Based on the standard for Total tribalomethanes of 100 ug/l. 

j. Based an criteria for polycyclic aromatic hydrocarbons (PAHs). 

k. Million fibers/liter. 

l. 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. 

† Secondary MCL. 

†† n = pCi/l. 

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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 

Freshwater Freshwater Marine Marine 

Acute Chronic Acute Chronic 

Criteria Criteria Criteria Criteria 

1,700b 520b 970b 710b 

68b 21b 55b S 

7,550b 2,600b S S 

3.0 S 1.3 S 

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

S 20,000 S 

CRITERIA ARE pH AND TEMPERATURE DEPENDENT 

9,000b 1,600b S 

850b 48b 2,319b 

360 190 69 

FOR PRIMARY RECREATION AND SHELLFISH USES 

5,300b S 5,100b 

2,500b S S 

130b 5.3b S 

100b S 0.34b 

3.9a 1.1a 43 

35,200b S 50,000b 

S 

S 

13b 

36 

700b 

S 

S 

S 

9.3 

S 

2.4 0.0043 0.09 0.004 

250b 50b 160b 129b 

1,600b S S 7.5b S 

19 11 13 7.5 

238,000b S S S 

28,900b 1,240b S S 

4,380b 2,000b S S 

S S 29,700b S 

30b S S S 

16 11 1,100 50 

1,700a 210a 10,300b S 

18a 12a 2.9 2.9 

22 5.2 1 1 

1.1 0.001 0.13 0.001 

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Table E-2 

(Continued) 

Concentration 

DDE

TDE

Demeton

Dichlorobenzenes

1,2-Dichlorethane

Dichloroethylenes

2,4-Dichlorophenol

Dichloropropane

Dichloropropene

Dieldrin

2,4-Dimethyl phenol

Dinitrotoluene

2,3,7,8-TCDD

1,2-Diphenylhydrazine

Endosulfan

Endrin

Ethylbenzene

Fluoranthene

Guthion

Haloethers

Halomethanes

Heptachlor

Hexachloroethane

Hexachlorobutadiene

Lindane

Hexachlorocyclopentadiene

Iron

Isophorone

Lead

Malathion

Mercury

Freshwater Freshwater Marine Marine 

Acute Chronic Acute Chronic 

Criteria Criteria Criteria Criteria 

1,050b S 14b S 

0.06b S 3.6b S 

S 0.1 S 0.1 

1,120b 763b 1,970b S 

118,000b 20,000b 113,000b S 

11,600b S 224,000b S 

2,020b 365b S S 

23,000b 5,700b 10,300b 3,040b 

6,060b 244b 790b S 

2.5 0.0019 0.71 0.0019 

2,120b S S S 

330b 230b 590b 370b 

<0.01b <0.00001b S S 

270b S S S 

0.22 0.056 0.034 0.0087 

0.18 0.0023 0.037 0.0023 

32,000b S 430b S 

3,980b S 40b 16b 

S 0.01 S 0.01 

360b 122b S S 

11,000b S 12,000b 6,400b 

0.52 0.0038 0.053 0.0036 

980b 540b 940b S 

90b 9.3b 32b S 

2.0 0.08 0.16 S 

7b 5.2b 7b S 

S 1,000 S S 

117,000b S 12,900b S 

82a 3.2a 140 5.6 

S 0.01 S 0.01 

2.4 0.012 2.1 0.025 

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Table E-2 

(Continued) 

Concentration 

Methoxychlor

Mirex

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 Freshwater Marine Marine 

Acute Chronic Acute Chronic 

Criteria Criteria Criteria Criteria 

S 0.03 S 0.03 

S 0.001 S 0.001 

2,300b 620b 2,350b S 

1,800a 96a 140 7.1 

27,000b S 6,680b S 

230b 150b 4,850b S 

5,850b S 3,300,000b S 

S 0.04 S 0.04 

2.0 0.014 10 0.03 

7,240b 1,100b 390b 281b 

55b 3.2b 53b 34b 

10,200b 2,560b 800 S 

940b 3b 2,944 3.4b 

S S 300b S 

260 35 410 54 

4.1a 0.12 2.3 – 

S 2 S 2 

9,320b S S S 

S 2,400b 9,020b S 

9,320b 

5,280b 840b 10,200b 450b 

S S S 440b 

1,400b 40b 2,130b S 

17,500b 6,300b 5,000b 

1.6 0.013 0.07 S 

18,000b S S S 

S S 31,200b S 

S 9,400b S S 

45,000b 21,900b 2,000b S 

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Table E-2 

(Continued) 

Concentration 

Freshwater Freshwater Marine Marine 

Acute Chronic Acute Chronic 

Criteria Criteria Criteria Criteria 

2,4,6-Trichlorophenol – 970b – – 

Zinc 320a 47 170 

aHardness dependent criterion (100 mg/l used).

bInsufficient data to develop criteria. Value presented is the L.O.E.L.--lowest observed effect level.

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58 
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 subsequent 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 requested 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 quality 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 consequences of denying access to EPA; 

[7] special considerations that you have requested. 

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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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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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, 

requiring 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 adequate 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 adequate monitoring is 

conducted to determine the level of protective clothing required 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 quality 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 request, 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 

required. 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 request. 

[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. 

jU.S. GOVERNMENT PRINTING OFFICE: 1989-648-163/87077 

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