EPA/540/R-92/OC4
                           Publication 9285.7-01 C
                               December 1991
Risk Assessment Guidance
       for Superfuncl:
         Volume I —
 Human Health Evaluation
           Manual
(Part  C, Risk Evaluation of
   Remedial Alternatives)
            Interim
 Office of Emergency and Remedial Response
    U.S. Environmental Protection Agency
        Washington, DC 20460
                          Printed on Recycled Paper

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                                            NOTICE
        The policies set out in this document are intended solely as guidance; they are not final U.S.
Environmental Protection Agency (EPA) actions.  These policies are not intended, nor can they be relied
upon, to create any rights enforceable by any party in litigation with the United States. EPA officials may
decide to follow the guidance provided in this document, or to act at variance with the guidance, based on an
analysis of specific site circumstances. The Agency also reserves the right to change this guidance at any time
without public notice.

        This guidance is based on policies in the Final Rule of the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP), which was published on  March 8, 1990 (55 Federal Re&ster 8666). The
NCP should be considered the authoritative source.
                                               -11-

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                                  CONTENTS
                                                                              Page
NOTICE	. . . .		ii

EXHIBITS	-v

DEFINITIONS	. . . .	,	 -	  vi

ACRONYMS/ABBREVIATIONS	  viii

ACKNOWLEDGEMENTS			• • • xi

PREFACE					xii

1.0     INTRODUCTION ..	 .	• • 1

       1.1  SCOPE AND OVERVIEW OF PART C	 1

           1.1.1  Scope	1
           1.1.2  Overview			3

       1.2  RELEVANT STATUTES, REGULATIONS, AND GUIDANCE . . .	 6

           1.2.1  CERCLA/SARA		'.'	6
           1.2.2  NCP . .		,6
           1.2.3  Other Relevant Guidance	7

       1.3  LEVEL OF EFFORT 	.'	7

       1.4  IMPORTANCE OF RISK COMMUNICATION	 . .	7

       1.5  MANAGEMENT AND DOCUMENTATION	8

       1.6  ORGANIZATION OF THE DOCUMENT		8

2.0     RISK EVALUATION DURING THE FEASIBILITY STUDY		  11

       2.1  RISK EVALUATION DURING DEVELOPMENT AND SCREENING
           OF ALTERNATIVES	 . .	11

           2.1.1  Consideration of Long-term Human Health Risks	• •  11
           2.1.2  Consideration of Short-term Human Health Risks	  11

       2.2  RISK EVALUATION DURING DETAILED ANALYSIS OF ALTERNATIVES	12

           2.2.1  Evaluation of Long-term Human Health Risks for Detailed Analysis  	 14
           2.2.2  Evaluation of Short-term Human Health Risks for Detailed Analysis	 15

       2.3  CASE STUDIES		-••	20

3.0    RISK EVALUATION AFTER THE FEASIBILITY STUDY	;	 - 25

       3.1  RISK EVALUATION FOR THE PROPOSED PLAN .	 25
                                        -111-

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                                CONTENTS (Continued)
                                                                                  Page
       3.2  DOCUMENTATION OF RISKS IN THE ROD  	25

       3.3  RISK EVALUATION DURING REMEDIAL DESIGN/REMEDIAL ACTION	25

            3.3.1  Risk Evaluation During Remedial Design	26
            3.3.2  Monitoring Short-term Health Risks During Implementation	26
            3.33  Assessing Attainment of Selected Remediation Levels
                 During implementation 	,               26
            3.3.4  Evaluation of Residual Risk	-.	26

       3.4  RISK EVALUATION DURING FIVE-YEAR REVIEWS	 . 27

            3.4.1  Purpose of Five-year Reviews .,	27
            3.4.2  Sites That Receive Five-year Reviews	'.'.'.'.'. 27
            3.4.3  Risk-related Activities During Five-year Reviews	28

REFERENCES	        29

APPENDIX A     SELECTED REMEDIATION TECHNOLOGIES AND ASSOCIATED
                 POTENTIAL RELEASES	31

APPENDIX B     QUANTIFYING POTENTIAL RELEASES FROM SELECTED
                 REMEDIATION TECHNOLOGIES	43

       B.I  SOILS HANDLING TECHNOLOGIES  	43

       B.2  THERMAL DESTRUCTION TECHNOLOGIES 	43

       B.3  SOLIDIFICATION/STABILIZATION TREATMENT TECHNOLOGIES	 44

       B.4  REFERENCES FOR DETERMINING RELEASES RESULTING FROM REMEDIAL
            ACTIVITIES	        ;      45

            B.4.1  Various Remedial Activities	     45
            B.4.2  Soils Handling	'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'. 45
            B.4.3  Thermal Destruction  	45
            B.4.4  Stabilization/Solidification  	47

APPENDIX C     SHORT-TERM TOXICITY VALUES	49

       Cl  BACKGROUND ON EXPOSURE DURATION  	49

       C.2  EXISTING SHORT-TERM TOXICITY VALUES '.	50
                                      >»
            C2.1  Toxicity Values for Assessing Risk of Noncarcinogenic Effects for Short-term
                 Exposure	           50
            C.2.2  Specific Carcinogenic Risk Values for Short-term Exposures  		54
APPENDIX D
RADIATION REMEDIATION TECHNOLOGIES	  	57
                                         -IV-

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                                EXHIBITS

 Exhibit                                                                 Page

 1-1   RELATIONSHIP OF HUMAN HEALTH EVALUATION TO THE
      CERCLA PROCESS 	,	2

 1-2   SUMMARY OF RISK EVALUATIONS OF REMEDIAL
      ALTERNATIVES .	 .	4

 1-3   RISK EVALUATION OF REMEDIAL ALTERNATIVES IN
      THE CERCLA PROCESS	.	5

" 2-1   ILLUSTRATION OF AN EXPOSURE PATHWAY FOR A REMEDIAL ACTION	17

 2-2   ILLUSTRATION OF CUMULATIVE EXPOSURES FROM MULTIPLE RELEASES.	18

 A-l   REMEDIATION TECHNOLOGY DESCRIPTIONS	r	.32

 A-2   REMEDIATION TECHNOLOGIES AND SOME POTENTIALLY
      SIGNIFICANT RELEASES	 37

 D-l   POTENTIAL RELEASES OF RADIOACTIVITY ASSOCIATED WITH
      RADIATION REMEDIATION TECHNOLOGIES	 58

 D-2   DEGREE OF POTENTIAL SHORT- AND LONG-TERM RISKS ASSOCIATED
      WITH RADIATION REMEDIATION TECHNOLOGIES	 62
                                     -v-

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                                         DEFINITIONS
              Term
                          Definition
 Applicable or Relevant and
 Appropriate Requirements
 (ARARs)
Exposure Pathway
Exposure Point
Exposure Route
Final Remediation Levels
Long-term Risks
Preliminary  Remediation  Goals
(PRGs)
 "Applicable" requirements are those clean-up 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
 Comprehensive  Environmental  Response,  Compensation,  and
 Liability  Act (CERCLA)  site.    "Relevant  and  appropriate"
 requirements  are  those  clean-up  standards  which,  while not
 "applicable" at a CERCLA site,  address problems  or situations
 sufficiently similar to those encountered at the  CERCLA site that
 their use is well-suited to the particular site. ARARs can be action-
 specific, location-specific, or chemical-specific.

 The course a chemical or physical agent takes from a source to an
 exposed organism.  An exposure  pathway describes  a unique
 mechanism  by which an individual or population is exposed to
 chemicals or physical agents at or originating  from a site.  Each
 exposure pathway  includes a source or release from a source, an
 exposure point, and an exposure route. If the exposure point differs
 from the source, a transport/exposure medium  (e.g., air) or media
 (in cases of intermedia transfer) also would be indicated.

 A location of potential contact between an organism and a chemical
 or physical agent.

 The way a chemical or  physical agent comes in contact with an
 organism (i.e., by ingestion, inhalation, dermal contact).

 Chemical-specific  clean-up  levels  that are  documented in the
 Record of Decision (ROD). They may differ from preliminary
 remediation goals (PRGs). because of modifications resulting from
 consideration  of various  uncertainties,  technical and exposure
 factors, and all nine selection-of-remedy criteria outlined in the
 National Oil and Hazardous Substances Pollution Contingency Plan
 (NCP).

 Risks that remain  after  remedy implementation is complete (i.e.,
 residual risks).

 Initial clean-up goals that (1) are protective of human health and
 the environment and (2)  comply with ARARs. They are developed
early in the process based on readily available information and are
modified to  reflect results of the baseline risk  assessment. They
also are  used during analysis  of remedial alternatives  in  the
 remedial investigation/feasibility study (RI/FS).
                                               -VI-

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                                  DEFINITIONS (Continued)
             Term
                          Definition
Remedial Alternative
Remedial Action

Risk-based Concentrations
Short-term Risks
An action considered in the feasibility study intended to reduce or
eliminate significant risks to human health and/or the environment
at a site. A range of remedial alternatives are considered in detail
by the FS while the selection of a specific remedial alternative over
others is documented in the ROD.

The selected alternative that is documented in the ROD.

Concentration levels for individual chemicals that correspond to a
specific cancer risk level (e.g., 10"6, 10"4) or hazard quotient (HQ)
or hazard index (HI) (e.g.,  less than or equal to 1).  They are
generally selected as preliminary or final remediation goals when
ARARs are not available.

Risks that occur during implementation of a remedial alternative.
Some "short-term" risks can occur over a period of many years (e.g.,
risk associated with air stripper emissions).
                                                -Vll-

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                             ACROlSfYMS/ABBREVIATIONS
      Acronym/

     Abbreviation
                              Definition
 ACGIH



 AIC



 APCD



 ARARs



 ATSDR



 CEGL



 CERCLA



 CFR



 ECAO



 EEGL



 EPA



 HEAST



 HHEM



 HI



 HQ



 IDLH



 IRIS



 LOAEL



 MCL



MRL



NCP



NIOSH



NOAEL



NRC
 American Conference of Governmental Industrial Hygienists




 Acute Inhalation Criteria




 Air Pollution Control Device.
                                j



 Applicable or Relevant and Appropriate Requirements




 Agency for Toxic Substances and Disease Registry




 Continuous Exposure Guidance Level




 Comprehensive Environmental Response, Compensation, and Liability Act




 Code of Federal Regulations




 Environmental Criteria and Assessment Office




 Emergency Exposure Guidance Level




 U.S. Environmental Protection Agency




 Health Effects Assessment Summary Tables




 Human Health Evaluation Manual




 Hazard Index




 Hazard Quotient




 Immediately Dangerous to  Life and Health




 Integrated Risk Information System




 Lowest-observed-adverse-effect-level




Maximum Contaminant Level




Minimal Risk Level




National Oil and Hazardous Substances Pollution Contingency Plan




National Institute for Occupational Safety and Health




No-observed-adverse-effect-level




National Research Council
                                           -via-

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                      ACRONYMS/ABBREVIATIONS (Continued)
     Acronym/
    Abbreviation
                             Definition
ORD

OSHA

PEL

POTW

PPE

PRO

QA/QC

RAGS

RCRA

REL

RfC

RfD

RI/FS

RME

ROD

RPM

RQ

RREL

SARA

SPEGL

TLV-C

TLV-STEL

TLV-TWA

TSC
Office of Research and Development

Occupational Safety and Health Administration

Permissible Exposure Level

Publicly Owned Treatment Works

Personal Protective Equipment

Preliminary Remediation Goal

Quality Assurance/Quality Control

Risk Assessment Guidance for Superfund

Resource Conservation and Recovery Act

Recommended Exposure Level

Reference Concentration

Reference Dose

Remedial Investigation/Feasibility Study

Reasonable Maximum Exposure

Record of Decision

Remedial Project Manager

Reportable Quantity

Risk Reduction Engineering Laboratory

Superfund Amendments and Reauthorization Act

Short-term Public Emergency Guidance Level

Threshold Limit Values - Ceiling

Threshold Limit Values - Short-term Exposure Limit

Threshold Limit Values - Time-weighted Average

Superfund Health Risk Technical Support Center
                                            -IX-

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                    ACRONYMS/ABBREVIATIONS (Continued)
     Acronym/
   Abbreviation
                          Definition
TSCA

VOCs
Toxic Substances Control Act

Volatile Organic Compounds
                                        -x-

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                                ACKNOWLEDGEMENTS
       This manual was developed by the Toxics Integration Branch (TIB) of EPA's Office of Emergency and
Remedial Response, Hazardous Site Evaluation Division. A large number of EPA regional and headquarters
managers and technical staff (see below) provided valuable input regarding the organization, content, and
policy implications of the manual throughout its development.

       ICF Incorporated provided technical assistance to EPA in the development of this manual, under
Contract Nos. 68-01-7389,68-W8-0098, and 68-03-3452.  S. Cohen and Associates (SC&A) provided assistance
in the development of Appendix D, under EPA Contract No. 68-D9-0170.
                                      WORKGROUP
                                     EPA HEADQUARTERS
Office of Emergency and Remedial Response:
Office of Radiation Programs:
Office of General Counsel:
Office of Policy, Planning, and Evaluation:
Office of Waste Programs Enforcement:
Office of Health and Environmental Assessment:
Rhea Cohen, David Cooper,
Steve Golian, Jennifer Sutler, Ed Hanlon,
James Konz, Tracy Ldy, Bruce Means
Bob Dyer
Larry Starfield
Pepi Lecayo
Steve Ells
Kevin Garrahan
                                   EPA REGIONAL OFFICES
Region 1:
Region 5:

Region 6:
Region 10:
Ann-Marie Burke, Jeri Weiss
Alison Hiltner, Jae Lee,
Andrew Podowski
Jon Rauscher
Judi Schwarz, Carol Sweeney
                                     OTHER EPA OFFICES
 Risk Reduction Engineering Laboratory:
 Office of Air Quality Planning and Standards:
 Office of Health and Environmental Assessment:
                                       STATE AGENCIES
 Michigan Department of Natural Resources:
 New Jersey Department of Environmental Protection:
Pat Lafornara
Fred Hauchman
Pei-Fung Hurst
Chris Flaga
Linda Cullen
                                               -XI-

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                                          PREFACE
        Risk Assessment Guidance for Superjund:   Volume I  —  Human  Health Evaluation Manual
(RAGS/HHEM) Part C is one of a three-part series. Part A addresses the baseline risk assessment; Part B
addresses the development of risk-based preliminary remediation  goals.  Part C provides guidance on the
human health risk evaluations of remedial alternatives that are conducted during the feasibility study, during
selection and documentation of a remedy, and during and after remedy implementation.  Part C provides
general guidance to  assist in site-specific risk  evaluations and to maintain flexibility in the analysis and
decision-making process. This guidance does not discuss the evaluation of ecological effects that takes place
during remedy selection and implementation, nor does  it discuss  the risk management decisions that are
necessary at a CERCLA site (e.g., selection of final remediation goals). The potential users of Part C are
persons involved in the remedy selection and implementation process, including risk assessors, risk assessment
reviewers, remedial project managers, and other decision-makers.

        This manual is being distributed as  an  interim document to allow for a period of field testing and
review.  RAGS/HHEM will be revised in the future, and Parts A, B, and C will be incorporated into a single
final guidance document. Additional information for specific subject areas is being developed for inclusion
in a later revision. These areas include:

        •      development of short-term inhalation toxicity values;
        •      short-term worker health and safety issues; and
        •      determination of attainment of final remediation goals.
        Comments addressing usefulness, changes, and additional areas where guidance is needed should be
sent to:
               U.S. Environmental Protection Agency
               Toxics Integration Branch (OS-230).
               Office of Emergency and Remedial Response
               401 M Street, SW
               Washington, DC 20460
               Telephone:
               FAX:
202-260-9486
202-260-6852
                                               -Xll-

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                                     CHAPTER  1

                               INTRODUCTION
    This guidance has been developed by the U.S.
Environmental Protection Agency (EPA) to assist
remedial project managers  (RPMs), risk assessors,
site engineers, and others in using risk information
at  Comprehensive  Environmental  Response,
Compensation, and Liability Act (CERCLA) sites
to both evaluate remedial  alternatives  during the
feasibility study (FS) and to evaluate the human
health risk associated with the selected remedial
alternative  during and  after its  implementation.
Part C provides general guidance to assist in site-
specific risk evaluations and to maintain flexibility
in the decision-making process.

    Risk assessment is one of many  tools that
RPMs use in selecting the best remedy for a site.
Other important tools  (not addressed  in  this
guidance)  involve  the  assessments of technical
feasibility, applicable or relevant and appropriate
requirements   (ARARs),   cost,   and
implementability.

    This guidance is the third part (Part C) in the
series Risk Assessment Guidance for  Superfund:
Volume I — Human Health Evaluation Manual
(RAGS/HHEM). Part A  of this guidance (EPA
1989g) describes how to  conduct  a site-specific
baseline risk assessment; the information in Part A
is necessary background for Part  C.  Part B (EPA
1991c) provides guidance for calculating risk-based
concentrations  that may  be  used, along  with
ARARs  and  other  information, to  develop
preliminary remediation  goals  (PRGs) during
project scoping.  PRGs  (and final remediation
levels set in the Record of Decision [ROD]) can
be used throughout the analyses in Part C to assist
in evaluating the human health risks of remedial
alternatives.   Exhibit 1-1  illustrates  the major
correspondence of RAGS/HHEM  activities with
the steps in the CERCLA remedial process.

  ,  The steps for conducting a risk evaluation of
remedial alternatives are discussed in general terms
in Chapters 2 and 3; more detailed guidance for
conducting short-term evaluations  is provided in
Appendices A through D.  (See the box in the next
column for a description  of how the terms short-
   SHORT-TERM RISK VS. LONG-TERM RISK

       For the purposes of this guidance, short-term
   risks are those that occur during implementation of
   a remedial alternative. Some "short-term" risks can
   occur over  a  period of  many years (e.g., risk
   associated with air stripper emissions). In contrast,
   long-term risks are those that remain after remedy
   implementation is complete (i.e., residual risks).
term  risk  and  long-term  risk differ  in  this
guidance.) The remainder of this chapter:

•   presents the scop&and an overview of Part C;

•   discusses  the  statutes,   regulations,  and
    guidance  relevant  to   the evaluation  of
    remedial alternatives;

•   describes appropriate levels of effort for risk
    evaluations of remedial alternatives;

•   discusses    the   importance   of   risk
    communication;

•   addresses the role of the RPM and the  need
    for documentation; and

•   presents the organization of the remainder of
    this document.

1.1     SCOPE AND OVERVIEW OF
        PARTC

1.1.1    SCOPE

    As discussed in Section 1.2 below, some of the
nine criteria that are described in the National Oil
and Hazardous Substances Pollution Contingency
Plan (NCP) and that are used to evaluate remedial
alternatives  during the  remedial  investigation/
feasibility study (RI/FS), involve a direct use of
risk-related information.  Several aspects of these
criteria (e.g.,  short-term risks to  workers and
                                                -1-

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                               EXHIBIT 1-1

         RELATIONSHIP OF THE HUMAN HEALTH EVALUATION
                       TO THE CERCLA PROCESS
CERCLA REMEDIAL PROCESS
   Scoping




Remedial
Investigation


Fusibility
Study
-


Remedy Selection
and Record of
Decision


Remedial Design/
Remedial Action


Deletion/
Five-year Review
HUMAN HEALTH EVALUATION MANUAL
               PART A
          Baseline Risk Assessment
           PARTB
      Development of Risk-based
     Preliminary Remediation Goals
                                        PARTC
                                Risk Evaluation of Remedial Alternatives
                                  -2-

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surrounding community, long-term effectiveness)
are discussed  in detail in this guidance.  Other
criteria that do not  directly  involve health risk
(e.g., implementability, cost) — with the exception
of community acceptance — are mentioned briefly
but are not discussed in detail.

    Remedial  alternatives,  in addition  to  being
evaluated for  the degree to  which they protect
human health, are evaluated for their potential to
protect  ecological  receptors.    RAGS/HHEM
Part C does not address ecological risk assessment
(see the next box).  However, ecological guidance
specific to evaluating remedial alternatives in the
CERCLA program will be developed following
finalization of Agency guidance on ecological risk
assessment.
    EVALUATING ECOLOGICAL EFFECTS OF
           REMEDIAL ALTERNATIVES

        Remedial actions, by their nature, can alter
   or destroy aquatic and terrestrial habitat.  This
   potential for destruction or alteration of habitat
   and subsequent consequences must be evaluated
   so that it can be considered during the selection of
   a   remedial   alternative  and   during   its
   implementation.

        This document does  not  address   the
   evaluation of ecological risks. Future guidance for
   ecological evaluations is planned, however.   At
   present, ecological evaluations should be based on
   the best  professional judgment of experienced
   ecologists  and/or  aquatic  or  environmental
   toxicologists.
    The guidance in this document applies to sites
contaminated  with  non-radioactive  hazardous
substances   and    those   contaminated   with
radionuclides.  Appendix  D  provides additional
guidance specific to radionuclide sites.

    Note that this guidance is limited to the use of
risk assessment in evaluating remedial alternatives.
Part C does  not  provide guidance on the risk
management decisions  that must be made when
evaluating alternatives and selecting a remedy (e.g.,
balancing of the nine NCP criteria, selection of
final remediation goals and levels) or engineering
judgments that affect the evaluation of alternatives
(e.g., determining whether an alternative is likely
to achieve remediation goals). ' These issues are
addressed in other guidance or in guidance that'
currently is being developed.

1.1.2    OVERVIEW

    The process of evaluating remedial alternatives
begins in the development and screening stage of
the FS and extends into the detailed analysis stage.
The major goal for the risk evaluation during these
steps  is to provide decision-makers with specific
information that they may need in choosing among
alternatives. Additional risk evaluations may need
to be conducted during the proposed plan, during
the design and implementation of the remedy, and
after the remedy is complete (e.g., during "five-year
reviews"). These activities are discussed below and
throughout this guidance.

    Exhibit 1-2 summarizes the levels of effort, and
purposes  of the  risk  evaluations   of  remedial
alternatives, while  Exhibit 1-3 illustrates when
these activities take place within the context of the
CERCLA remedial process.

    Identification and Screening of Technologies
and Alternatives.  During this stage, a range of
remedial alternatives is identified, if necessary, and
each  alternative is evaluated  with  respect  to
effectiveness, implementability,  and cost.   This
process may consist of two steps: (1) identification
and screening of technologies and (2) development
and screening  of alternatives.  These steps  are
often combined into a single step (as reflected in.
this guidance).  Those alternatives that are clearly
unfavorable relative to other alternatives in terms
of effectiveness (e.g., very high perceived risk) or
implementability, or that are grossly excessive in
cost are dropped from  consideration  after this
screening.  Part of the evaluation  of effectiveness
involves human  health  risk  (e.g.,  risks  to  the
community and remediation workers), and Chapter
2 of this document provides guidance on evaluating
these factors.   RAGS/HHEM Part  C does  not
discuss evaluating factors such as implementability
and cost.

    Detailed Analysis of Alternatives. During the
detailed analysis stage, alternatives are evaluated
according to each  of the nine NCP evaluation
criteria, and then are compared  to each  other.
Both  long-term effectiveness (i.e., residual risk)
and short-term effectiveness  (i.e.,  risk  to  the
community  and  remediation  workers  during
remedy implementation) are evaluated during the
detailed analysis.  Chapter 2 and Appendices A
                                                  -3-

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                                                              EXHIBIT 1-2

                            SUMMARY OF RISK EVALUATIONS OF REMEDIAL ALTERNATIVES
STAGE
Screening of
Alternatives
(Section 2.1) •
Detailed Analysis
of Alternatives
(Section 2.2)
Proposed Plan
(Section 3.1)
Record of Decision
(Section 3.2)
. Remedial Design
(Section 3.3)
Remedial Action
(Section 3.3)
Five-year Review
(Section 3.4)
LEVEL OF EFFORT
Short-term
Risk*
Qualitative
Qualitative or
Quantitative"1
Qualitative or
Quantitative11
Qualitative or
Quantitative"1
Qualitative or
Quantitative"1
Quantitative
Generally not
applicable
Long-term
Risk
Qualitative
Qualitative or
Quantitatived
Qualitative or
Quantitative"1
Qualitative or
Quantitative11
Qualitative or
Quantitative"1
Quantitative
Quantitative
PRIMARY PURPOSE OF RISK EVALUATION1
Short-term Risk'
Identify (and eliminate from consideration)
alternatives with clearly unacceptable short-term
risks.
Evaluate short-term risks of each alternative to
community and on-site remediation workers
during implementation so that these risks can be
compared among alternatives.
Refine previous analyses, as needed, based on
newly developed information.
Document short-term risks that may occur
during remedy implementation.
Refine previous analyses, as needed, and
identify need for engineering controls or other
measures to mitigate risks.
Ensure protection of workers and community by
monitoring emissions or exposure
concentrations, as needed.
Generally not applicable.
Long-term Risk
Identify (and eliminate from consideration)
alternatives with clearly unacceptable long-term risks.
Evaluate long-term (residual) risk of each alternative
and its ability to provide continued protection over
time so that these risks can be compared among
alternatives.
Refine previous analyses, as needed, based on newly
developed information.
Document risks that may remain after completion of
remedy and determine need for five-year reviews.
Refine previous analyses, as needed, and identify
need for engineering' controls or other measures to
mitigate risks.
Evaluate whether remediation levels specified in
ROD have been attained and evaluate residual risk
after completion of remedy to ensure protectiveness.
Confirm that remedy (including any engineering or
institutional controls) remains operational and "
functional and evaluate whether clean-up standards •
are still protective.
a Level of effort (i.e., qualitative or quantitative) refers only to the level of risk evaluation that is generally expected.  Levels other than those presented here, or
combinations of levels, are possible.  See the main text of this document for additional discussion on level of effort.

b Purpose presented in this exhibit for each stage is only the primary purpose; other purposes may exist.  See the main text of this document for additional information:

0 Short-term risk refers to risks that occur during remedy implementation.

d Text box in Section 2.2 lists considerations for deciding whether a qualitative or quantitative risk evaluation is needed for these stages.  •

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                           EXHIBIT 1-3

         RISK EVALUATION OF REMEDIAL ALTERNATIVES IN THE
                        CERCLA PROCESS
STAGES IN REMEDIATION
Remedial
investigation



Feasibility
Study





Selection of
Remedy




Remedial Design/
Remedial Action




Deletion/
Five-year Review


Evaluate Risks
During Screening
and Detailed
Analysis of
Alternatives




Develop Proposed
Plan and
Document Risks
of Alternatives
in Record of
Decision






Evaluate Risks
During Remedial
Design/Remedial
Action



Revisit
Protectiveness

Evaluate Attainment of
Final Goals and
Residual Risk




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 through D of this document provide guidance on
 the evaluation of the risk-related aspects of long-
 term effectiveness (residual risk and permanence),
 and short-term  effectiveness.    (As  with the
 screening of alternatives, Chapter 2 generally does
 not discuss evaluation of the other criteria, which
 do  not  directly  involve human  health  risk
 considerations.)  The resulting risk information is
 incorporated  into the  overall detailed analysis
 process described in the Guidance for Conducting
 Remedial Investigations and  Feasibility  Studies
 Under CERCLA (RI/FS Guidance; EPA 1988c).

    Proposed Plan and ROD. Risk evaluations are
 generally conducted during the development of the
 proposed  plan   and  ROD  only  when   new
 information  concerning risks of  the remedial
 alternatives is generated.  Chapter 3 provides
 guidance on  the evaluation  of  risks for the
 proposed plan and ROD stage.

    Remedial Design/Remedial Action  (RD/RA).
 Risk-related evaluations may also be conducted for
 some sites during implementation of the selected
 remedy.   These activities, discussed briefly in
 Chapter 3, include: (1) refining risk evaluations as
 necessary  when   designing  the  remedy;
 (2) monitoring potential short-terra health impacts
 on the community  and workers;  (3)  assessing
 attainment of final remediation levels selected in
 the ROD; and (4) evaluating residual risk.

    Five-year Review. Under the NCP, five-year
 reviews are required for sites as long as hazardous
substances remain onsite above levels that allow
 unlimited use and unrestricted exposure, and are
also conducted as a matter of policy for long-term
remedial  action  sites  even   if  no  hazardous
substances are expected to remain after completion
of the  action.  Chapter 3 briefly  addresses the
consideration of risk  during five-year reviews.

1.2    RELEVANT STATUTES,
        REGULATIONS, AND
        GUIDANCE

    As discussed in RAGS/HHEM Part A, there is
a  hierarchy of  requirements  and  guidance in
CERCLA, beginning'with the laws enacted by
Congress, followed by the regulations, and then the
guidance  developed  by  EPA.    This section
addresses this hierarchy within the context of the
risk evaluation of remedial alternatives.
 1.2.1   CERCLA/SARA

     CERCLA,  commonly called Superfund,  was
 enacted by Congress in 1980 in response to the
 dangers posed by sudden or otherwise uncontrolled
 releases of hazardous  substances, pollutants, or
 contaminants   into  the  environment.    The
 Superfund Amendments and Reauthorization Act
 (SARA) was enacted in 1986.  (All references to
 CERCLA in this guidance should be interpreted as
 "CERCLA as amended by SARA.")

    Section   121  of   CERCLA  requires  that
 remedies  be protective of human health and the
 environment, satisfy ARARs, be cost-effective, and
 utilize  permanent solutions  and  alternative
 treatment technologies to the  maximum extent
 practicable.  Section 121(c) of CERCLA requires
 a periodic review of remedial actions, at least every
 five years  after initiation, for  as long as hazardous
 substances that may pose a threat to human health
 or the  environment remain at the site.   The
 information in this manual provides  guidance for
 evaluating  the   protectiveness  of   remedial
 alternatives at a site in terms of the human health-
 related aspects  of these CERCLA requirements.
 Some   considerations   include  protectiveness,
 effectiveness in terms of risk reduction, and degree
 of hazard  for substances remaining at the site.

 1.2.2    NCP

   The NCP  is  the  main set of regulations
developed by EPA to implement CERCLA.  The
most recent NCP was published on March 8, 1990
 (55 Federal Register 8666-8865) and is codified at
40 Code of Federal Regulations  (CFR) Part 300.
Section 300.430(e)(l) of the NCP describes a two-
stage evaluation  of remedial  alternatives:   a
screening evaluation of a range of alternatives, if
necessary,  followed by a detailed analysis of the
most promising alternatives.   The NCP  also
describes  activities that  follow selection  and
implementation   of   the   selected   remedial
alternative.

   Screening.     NCP  section  300.430(e)(7)
indicates  that,  if necessary  and to  the  extent
sufficient  information  is available,  alternatives
should  be screened out  if determined  to  be
ineffective, not implementable, or grossly excessive
in cost.   Some aspects of effectiveness involve
considerations of  human  health  risk  and are
discussed in this guidance.
                                               -6-

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    Detailed Analysis.  The NCP establishes nine
criteria in section 300.430(e)(9)(iii) to  use in
evaluating alternatives in detail and in selecting a
remedy.  Parts of three of these criteria — overall
protection of human health and the environment,
long-term effectiveness and permanence, and short-
term effectiveness — directly relate  to risks and
therefore are the focus of this guidance.   The
actual  selection of a remedy for  any given site
ultimately is  based on consideration of the nine
criteria.    This   guidance also  discusses  the
importance   of  risk   communication   to  the
community  as  it  relates to  the  criterion of
community acceptance.

    Five-year   Reviews.     NCP   section
300.430(f)(4)(ii)  provides that  if   a  remedial
alternative is selected that results in hazardous
substances  (or   pollutants   or  contaminants)
remaining at the site above levels that allow for
unrestricted  exposure  and unlimited use, such
remedy should be reviewed at least every five years
after initiation of the selected remedial alternative.

1.2.3    OTHER RELEVANT GUIDANCE

    Three CERCLA  program  documents  are
important background for the guidance presented
in this document — RAGS/HHEM Parts A and B
(EPA 1989g; EPA 1991c), and the RI/FS Guidance
(EPA 1988c). Parts A and B provide guidance on
conducting  a baseline risk  assessment  and on
developing risk-based concentrations, respectively,
that  should  be  used  in evaluating  remedial
alternatives.  The activities conducted during a risk
evaluation of remedial alternatives are somewhat
similar to the activities conducted during a baseline
risk assessment.  (Chapter 2  discusses  in more
detail the similarities and differences.) The RI/FS
Guidance  describes the  major  activities  and
analyses that are conducted during the RI/FS.  See
the references at the end of  this document for
other relevant background guidance.

 1.3     LEVEL OF EFFORT

     The  level of  effort  for  risk evaluations of
 remedial alternatives depends primarily on the site-
 specific questions that must be answered in order
 to select and implement a remedy.  In addition,
 site-specific  factors such as the complexity of the
 site, the number of alternatives considered for the
 site, the available resources,  and the amount of
 available data may affect the  level of effort.  In
 most  cases,  a qualitative rather  than a detailed
quantitative evaluation of both  long-term and
short-term risks is all that is needed to select the
most appropriate alternative. A quantitative risk
evaluation of remedial alternatives will not need to
be conducted for all sites. In all cases, the baseline
risk assessment provides much of the risk-related
information needed  for the detailed  analysis of
alternatives, especially for those alternatives that
involve limited or no action.

    For  many  sites,  the  risk  evaluations  of
remedial alternatives during the FS are conducted
in a   qualitative  manner.   That  is,  the  risk
evaluations during both the screening and detailed
analysis stages for these sites will not be at all
quantitative.  At other sites, a more quantitative
analysis of the long-term and/or short-term risks
associated with the remedial alternatives may be
needed during the  detailed  analysis.   In these
situations, the risk evaluation generally needs to
incorporate more site-specific information.

    A guiding principle is that the risk evaluation
should be tailored  to provide  the  RPM with
specific  information that  he  or she  needs for
supporting the selection or design of a remedy
(e.g., the relative risks associated with alternatives,
the alternatives  that best  meet the remediation
goals). Because of the differences in information
needs and available data for sites, in the complexity
of sites, and  in  available methods,  models, and
resources for evaluation, all of the components of
this guidance will not be applicable to all sites.

    Chapter 2 provides some additional factors to
consider when deciding on the level of effort to
use for the risk evaluation of remedial alternatives.

1.4    IMPORTANCE OF RISK
        COMMUNICATION

    As noted earlier,  while overall protection of
human health and the environment is one of the
threshold criteria established by the NCP for use in
evaluating alternatives and selecting  a remedy,
community  acceptance  of  the remedy  is   a
modifying criterion (NCP section 300.430(e) (9)
(iii)).   The  CERCLA program  encourages and
promotes public participation during all phases of
the  decision-making process  at  CERCLA sites.
Just as risk information is used by RPMs and other
EPA  staff to assist  in  evaluation of remedial
alternatives during  the FS and  to  evaluate the
selected remedial alternative during and after its
                                                  -7-

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 implementation, risk information also will  be
 employed by the public in their acceptance of a
 selected remedy. Good communication of the risks
 of the remedy to the public is crucial  to the
 community's acceptance of the remedy.

     There is  no single procedure for good risk
 communication.  The actual mechanism used and
 the messages  delivered will vary from site to site
 and will  depend upon the  public, their level  of
 concern,   the  complexity   of   the   site,  the
 contaminants  of concern,  and  the  proposed
 remedial alternative.   RPMs  are encouraged  to
 work  with the  risk  assessor  and  community
 relations  coordinator for the site to develop the
 appropriate means to communicate risks from the
 remedial  alternative or any residual risks.  RPMs
 should consider using fact sheets, public meetings,
 and  the  release of  draft  documents  or "risk
 communication" summaries as vehicles for risk
 communication.     Community   Relations   in
 Superfund:  A  Handbook  (EPA 1988a)  offers
 guidance  on planning and  conducting CERCLA
 community relations activities.

    Regardless of the vehicles  chosen for  risk
 communication, the following rules, from Seven
 Cardinal  Rules  of Risk Communication  (EPA
 1988Q, should be kept in mind.

 •   Accept and involve the public as a legitimate
    partner.

 •   Plan carefully and evaluate your efforts.

 •   Listen to the public's specific concerns.

 •   Be honest, frank, and open.

 •   Coordinate and collaborate with other credible
    sources.

 •   Meet  the needs of the media.

 •   Speak clearly and with compassion.

    As  provided  under   the   NCP,   risk
communication,  public   participation,   and
community relations at CERCLA sites  begin well
before the  remedy selection  phase.    This is
important, as  communities  near  CERCLA sites
may begin with a degree of outrage that  must be
addressed  before effective   communication  can
begin.  Community relations, public involvement,
and good risk communication continue throughout
 the RI/FS process.  A well-informed public will be
 better able to comment on — and provide input to
 — technical  decisions.   Establishing  credibility
 through community relations, public participation,
 and effective risk communication practices early in
 the CERCLA process leads to greater community
 acceptance of the selected remedy.

 1.5    MANAGEMENT AND
        DOCUMENTATION

     One role of an RPM in the risk evaluation of
 remedial alternatives is to make risk management
 decisions.  The RPM must have a comprehensive
 understanding of the risk evaluation in order to
 make these decisions.  The first box on the next
 page provides questions  that RPMs and other
 decision-makers should ask about  the risks of
 remedial alternatives at their sites.   The second
 box provides guidance on where to document the
 evaluations addressed in RAGS/HHEM Part C.

 1.6    ORGANIZATION OF THE
        DOCUMENT

    The remainder  of this guidance is organized
 into two additional chapters and four appendices,
 as follows:

 •   Chapter  2:   Risk  Evaluation  During  the
    Feasibility Study;

 •   Chapter  3:    Risk  Evaluation  After ,the
    Feasibility Study;

 •   Appendix  A:      Selected   Remediation
    Technologies  and   Associated   Potential
    Releases;

 •   Appendix B:   Guidance  for  Quantifying
    Potential Releases from Selected Remediation
    Technologies;

 •   Appendix C: Short-term Toxicity Values; and

 •   Appendix  D:     Radiation   Remediation
    Technologies.

In addition, several boxes,.such as those below,
provide  useful information. A second kind of box,
a "shadow" box, provides case studies.  These boxes
are presented at the end of Chapter 2.
                                               -8-

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  QUESTIONS RPMs SHOULD ASK ABOUT HUMAN HEALTH RISKS OF REMEDIAL ALTERNATIVES

    Which technologies can readily achieve all  preliminary remediation goals (PRGs) in a given medium?  What
    uncertainties are involved in this determination?

    Which alternatives will clearly not address the significant human exposure pathways identified in the baseline risk
    assessment?

    Are the expected residual risks or short-term risks from one alternative significantly different from another?

    What other risk-based benefits (e.g., shorter time to achieving goals) are realized by selecting one alternative over
    another?

    Will implementation of specific technologies create new chemicals of concern or new significant exposures or risks
    for the surrounding community?

    Is there a need for engineering controls or  other measures to mitigate risks during implementation?  Are such
    controls available?  How reliable are these  controls?

    Does the remedial alternative result in hazardous substances remaining at the site such that a five-year review or
    reviews would be required?
                              DOCUMENTATION OF RISK EVALUATIONS

•   The risk evaluation conducted during the development and screening of alternatives (Section 2.1) and during the
    detailed analysis of alternatives (Section 2.2) should be documented in the FS.

•   The proposed plan (Section 3.1) should contain a summary of the risk evaluations for the alternatives, including
    any new risk information identified during development of the proposed plan.

•   The ROD (Section 3.2) should contain the results of the risk evaluations of the alternatives and the preferred
    alternative, including any results developed since the proposed plan.

•   Any significant changes identified during RD/RA (Section 3.3) in the risk evaluations should be documented (e.g.,
    in a memorandum).

•   Each five-year review (Section 3.4) should contain a statement on protectiveness and, if necessary, a recalculation
    of risk and/or a new risk assessment.
                                                   -9-

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                                   CHAPTER 2

                 RISK  EVALUATION  DURING
                     THE  FEASIBILITY  STUDY
    The FS  generally is a two-step process  of
evaluating remedial alternatives: (1) screening, if
necessary, and  (2) a more detailed analysis for
those alternatives that pass the screening.  The
RI/FS   Guidance  provides   information   on
conducting  the FS  and  describes  all of  the
evaluations that are performed.  Some of these
evaluations pertain to human health risk, and the
guidance in   this  chapter  assists  in  these
evaluations.    (Ecological  effects  of  remedial
alternatives  —  not discussed in RAGS/HHEM
Part C — also must be considered during the FS.)

2.1    RISK EVALUATION DURING
       DEVELOPMENT AND
       SCREENING OF
       ALTERNATIVES

    The overall objective of the development and
screening  of  alternatives  is  to  identify   an
appropriate range of waste management options,
some of which  will be analyzed more fully in the
detailed analysis phase. This process usually takes
place relatively early in the RI/FS process, during
project  scoping  (before  the  baseline  risk
assessment is completed).

    The NCP  specifies  that  the long-term and
short-term aspects of three criteria — effectiveness,
implementability, and cost — should be used to
guide the development and screening of remedial
alternatives.  At screening, those alternatives that
are clearly unacceptable  in terms of effectiveness
or implementability or are grossly excessive in cost
may be eliminated from further consideration.

    Consideration  of   effectiveness   involves
evaluating the  long-term and short-term human
health risks —  among other factors — associated
with a  remedial alternative.   The criteria  of
implementability and cost are not related to risk
and, therefore,  are not discussed in this document.
2.1.1   CONSIDERATION OF LONG-TERM
       HUMAN HEALTH RISKS

    The long-term human health risks associated
with a remedial alternative are those risks that will
remain after the remedy is complete (i.e., residual
risks).  Evaluating long-term risks might ideally
include an assessment of the risks associated with
treatment  residuals and untreated wastes (for a
treatment-based remedy), or an evaluation of the
remedy's ability to provide protectiveness over time
(for a containment-based remedy). This approach
might simply involve comparing estimates of the
final concentrations that a remedy is  expected to
achieve in a medium with the PRGs  for those
chemicals in that medium. At the screening stage,
however, this evaluation typically is based on
professional judgment and the experience of the
CERCLA program staff. Quantifying residual risks
during screening generally is not necessary. For
example, a technology  may be evaluated during
screening for its potential to treat the  classes — or
treatability groups  — of chemicals present at the
site (e.g., volatile organics, halogenated organics,
non-volatile metals) rather than its ability to meet
chemical-specific PRGs.  See  Section 2.2.1 for
additional   information  on  long-term   risks
associated  with remedial alternatives.

2.1.2   CONSIDERATION OF SHORT-TERM
       HUMAN HEALTH RISKS

    The short-term human health risks.associated
with a remedial alternative are those  risks that
occur during implementation  of the remedial
alternative (e.g., risks  associated  with  emissions
from  an onsite air stripper).   Because some
remedies may take many years to complete, some
"short-term" risks may actually occur over a period
of many years. Populations that may be exposed to
chemicals during remedy implementation include:
(1)  people who live and work in the vicinity of the
site and  (2) workers  who are involved in site
remediation.  As with  the consideration of long-
term risks, this evaluation is based primarily on
                                             -11-

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 many simplifying assumptions and on professional
 judgment at the screening stage and is intended to
 identify  alternatives with  clearly  unacceptable
 short-term risks. See Section 2.2.2 and Appendices
 A and D for additional information on evaluating
 alternatives  for short-term risks during screening
 and development of alternatives.

 2.2    RISK EVALUATION DURING
        DETAILED ANALYSIS OF
        ALTERNATIVES

    The overall objective of the detailed analysis of
 alternatives   is  to  obtain  and   present  the
 information that is needed for decision-makers to
 select a  remedial  alternative for  a site.   This
 detailed analysis  usually takes place  during the
 later stages of the Rl/FS process (i.e.", near the end
 of  or after  the baseline risk assessment, when
 PRGs may have  been modified).  As discussed
 previously, two of the balancing criteria assessed
 during  the   detailed  evaluation  —  long-term
 effectiveness and short-term effectiveness —involve
 an  evaluation of risk.  In addition, these criteria
 are considered in evaluating the criterion of overall
 protection of human health and the environment.

    The risk evaluations of remedial alternatives
 involve the same general steps as the baseline risk
 assessment:     exposure   assessment,  toxicity
 assessment, and risk characterization.  The box on
 this page  discusses the connection between the
 baseline risk assessment and the risk evaluations of
 remedial alternatives.

    The guidance provided in this section assists in
 assembling  and   using  available   site-specific
 information  for the purpose  of completing the
 detailed   analysis   of  remedial   alternatives,
specifically the evaluation of criteria that pertain to
 human health risks. The box on the next page lists
several sources of information that can be used in
 the risk evaluations that are conducted during the
 RI/FS. The box on page 14 addresses the question
of whether a quantitative  evaluation  is needed.
The case studies at the end of this chapter-provide
examples  of a  qualitative and  a quantitative
evaluation of long-term and short-term risks during
the detailed analysis.
  CONNECTION BETWEEN THE BASELINE
 RISK ASSESSMENT AND THE RISK EVAL-
   UATION OF REMEDIAL ALTERNATIVES

    A risk evaluation of remedial alternatives
 follows the same general steps as a baseline risk
 assessment.  Detailed guidance on  each step is
 provided in RAGS/HHEM Part A, which must be
 reviewed and understood lav the risk assessor
 before a risk evaluation of remedial alternatives is
 conducted.  Note, however, that the baseline risk
 assessment  typically is more quantitative  and
 requires a  higher  level of effort than the  risk
 evaluation  of  remedial  alternatives.    Other
 differences (and similarities) are listed below.

 Evaluate Exposure (Fart A — Chapter 6)

 •   The source of releases for the baseline  risk
    assessment is untreated site contamination,
    while the source of releases for the evaluation
    of remedial alternatives is the remedial action
    itself (plus any remaining waste).

 •   Exposure   pathways   associated  with
    implementation of remediation  technologies
    may include  some pathways and populations
    that were not present (or of concern)  under
    baseline conditions.

 •  'The  evaluation  of  short-term exposures
    associated with remedial  alternatives may
    consider a number of different releases that
    occur over varying durations.

Evaluate Toxicity (Part A — Chapter 7)

•   The risk evaluation of remedial alternatives
    often involves less-than-lifetime exposures that
    require appropriate short-term toxicity values
    to characterize risk or hazard.

•   The risk evaluation of remedial alternatives
    may include an analysis of chemicals that were
    not present under baseline conditions (i.e.,
    created as a result of the remedial alternative).

Characterize Risks (Part A — Chapter 8)

•   A risk  evaluation of remedial  alternatives
    generally considers risks to onsite workers, as
    well as risks to the surrounding community.

•   There are additional uncertainties involved in
    evaluating risks of remedial alternatives that
    are  not considered  in the  baseline risk
    assessment (e.g., confidence in performance of
    remedies and patterns of predicted releases,
    confidence in attainment of clean-up levels).
                                                  -12-

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               SOURCES OF INFORMATION FOR RISK EVALUATIONS DURING THE FS

        Baseline Risk Assessment.  Much of the data collected during the baseline risk assessment can also be used
to calculate the long-term residual risk associated with a remedial alternative.  Some of the data may be applicable
to calculation of risks during the remedial action. Some of the information from the baseline risk assessment that may
be useful for analyzing the risks associated with the remedial alternative includes:

•    exposure setting, including exposed populations and future land use (RAGS/HHEM Part A, Section 6.2);

e    exposure pathways, including sources of contamination, chemicals of concern, fate and transport of chemicals
     after release, and exposure points (RAGS/HHEM Part A, Section 6.3);

•    general exposure considerations, including contact rate, exposure frequency, and duration (RAGS/HHEM
     Part A, Section 6.4);                                                        ,

•    exposure concentrations, including monitoring data, modeling results, and media-specific results
     (RAGS/HHEM Part A, Section 6.5);

•    estimates of chemical intake (RAGS/HHEM Part A, Section 6.6);

•    toxicity information (e.g., changes/additions to Integrated Risk Information System [IRIS]  and Health Effects
     Assessment Summary Tables [HEAST]) (RAGS/HHEM Part A, Chapter 7);

•    quantitation of risks (RAGS/HHEM Part A, Section 8.6); and

•    uncertainties associated with toxicity assessment, exposure assessment, and baseline risk characterization
     (RAGS/HHEM Part A, Sections 6.8, 7.6, and  8.5).

     Treatability Studies. Treatability investigations are site-specific laboratory or field studies, performed either with
laboratory screening, bench-scale, or pilot-scale study (see Section 5.3 of the RI/FS Guidance).  Generic studies for
technologies (e.g., those performed by a vendor) can also contain useful information. Treatability studies may provide
risk-related  data such as (1) information on short-term emissions and (2)  information on removal efficiencies of a
technology.  This information may be especially useful when considering innovative technologies. Guide to Conducting
Treatability Studies under CERCLA (under development by EPA's Risk Reduction Engineering Laboratory) provides
a  three-tiered  approach  to conducting treatability  studies during screening, selection, and design of remedial
alternatives.  Chapter 5 of the  RI/FS  Guidance, especially Section 5.6,  provides information  on evaluating  the
applicability of the treatability study results (e.g., determination of usefulness, documentation, usefulness of residual
information,, application of laboratory/ bench/pilot studies to full-scale system).

     Feasibility Studies or Other Analyses for Comparable Sites. If a risk evaluation of one of the alternatives being
considered was conducted during the FS (or later stages) for a site with similar wastes and similar conditions, some
of the information that was developed may be helpful in characterizing the short-term or long-term risks associated
with that alternative. This type of information should be examined carefully to determine .whether the analyses are
appropriate  for the site  currently  being  evaluated.  Differences  in the  types of hazardous substances present,
characteristics of environmental media, meteorological conditions, locations of receptors, or other factors could result
in large differences in the risk evaluation.

      The Engineering and Technical Support Center of EPA's Risk Reduction Engineering Laboratory (513-569-7406
or FTS 684-7406) can provide information concerning treatability studies and evaluations of remedial technologies.

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 FACTORS TO CONSIDER WHEN DECIDING
     WHETHER A QUANTITATIVE RISK
         EVALUATION IS NEEDED

    The decision  of whether  to  conduct  a
quantitative or qualitative risk evaluation depends
on:  (1) whether the relative short-term or long-
term effectiveness of alternatives is an important
consideration in selecting an alternative and (2) the
"perceived  risk" associated with  the alternative.
The perceived risk includes both the professional
judgment of the site engineers and risk assessors
and  the concerns of neighboring  communities.
Some  factors that generally  lead to a  higher
perceived risk are as follows:

•   close proximity of populations;

•   presence of highly or acutely toxic chemicals;

•   technologies with high release potential, either
    planned or "accidental";

•   high uncertainties in the nature of releases
    (e.g,, amount  or identity of  contaminants
    released) such as might  exist with use of
    certain innovative technologies;

•   multiple  contaminants   and/or  exposure
    pathways affecting the same individuals;

•   multiple releases occurring simultaneously
    (e.g., from  technologies operating in  close
    proximity);

*   multiple releases occurring  from remedial
    actions at several operable units  in  close
    proximity; and

•   releases occurring over long periods of time.

    If consideration of these  (or other) factors
leads to a high perceived risk for an alternative, a
more  quantitative evaluation, including emission
modeling and/or detailed treatability studies, may
be helpful in the decision-making process.  For
example, if  one  alternative  considered for a site
involves extensive excavation in an area that is very
close  to  residential  populations,  then  a  more
quantitative evaluation of short-term risks may be
needed to evaluate this alternative.  In addition,
other factors, such as available data and resources,
may affect  the  level of  detail  for these risk
evaluations.
2.2.1   EVALUATION OF LONG-TERM
        HUMAN HEALTH RISKS FOR
        DETAILED ANALYSIS

     Evaluation of the  long-term  human health
risks  associated  with  a  remedial  alternative
involves:     (1)   evaluating   residual   risk  and
(2) evaluating the alternative's ability to provide
protection over time.

     Evaluate  Residual  Risk.   Because PRGs
generally are based on chronic human health risk.
considerations (e.g., ARARs such as maximum
contaminant   levels   (MCLs),   or   risk-based
concentrations), they usually provide the standard
to use to evaluate long-term health risks. When
site engineers are  developing alternatives  and
determining whether  a technology  is capable of
achieving  PRGs, they  are  in  effect evaluating
residual risk.  (Therefore, the results from using
RAGS/HHEM Part  B  and  other guidance  on
remediation goals are very important for this part
of the analysis.)

     Most of the  time it  will  be sufficient for the
detailed analysis  to indicate  whether or not an
alternative has the potential to achieve the PRGs,
rather than to quantify the risk that will remain
after implementation  of the  alternative.  If more
detailed information concerning long-term risk is
needed to select an alternative (e.g., to determine
the  more  favorable  of  two  otherwise similar
alternatives), then it may be useful to determine
whether one alternative is more certain to achieve
the  PRGs than the other, whether (or to what
extent) one may be able to surpass (i.e., achieve
lower concentrations than) the PRGs, or whether
one may be able to achieve the goals in  a shorter .
time.

     Certain   remedial   technologies   (e.g.,
incineration) may produce new contaminants that
were not present  at  the site  under  baseline
conditions.    The risks  associated with  these
additional   substances    generally   should   be
evaluated.  Another consideration  in evaluating
the residual risk associated with some alternatives
is  the level of confidence in the  ability of the
remedy as a whole to  achieve the  site engineers'
predictions.  For some technologies (e.g., ground-
water extraction and treatment technologies), past
experience has indicated that, in some situations,
it  may  be difficult or impossible  to achieve the
predicted  goals.    This  information   on  the
                                                -14-

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uncertainty associated with an alternative may be
an important factor in selecting a remedy.

    After the individual technologies comprising a
remedial   alternative   have  been   examined
separately, then the alternative as a whole should
be examined to determine the extent to which it
meets the PRGs for all of the contaminated media
and all of the contaminants of concern.  Even if
PRGs will be met, potential cumulative effects on
human  health  due  to  multiple contaminants,
media, or exposures may need to be considered.  If
an alternative  will not  meet the PRGs for all
media or contaminants of concern or if cumulative
effects are a concern, this information should be
highlighted in the presentation of the results of the
detailed analysis.

    Evaluate   Protectiveness   Over   Time.
Evaluating -whether an  alternative  is  likely to
maintain the specified level of protectiveness over
time (often referred to as "permanence") involves
using expert engineering judgment.  In particular,
if an  alternative  relies   on  engineering  or
institutional  controls  to  reduce  or  eliminate
exposure to contaminated media, then the ability
of these controls to maintain protectiveness should
be considered.   These types of remedies provide
protection by reducing or eliminating exposure to
hazardous substances rather than eliminating the
hazardous  substances  or  reducing  their
concentrations, volumes, or toxicity.   Failure of
such  remedies  could lead  to  an  increase in
exposure and therefore  an increase in risk.  For
example,  if a  remedy  includes the  capping of
contaminated  soils,  then  the potential  future
exposures due to cap failure include direct contact
with soils  and  the leaching of contaminants to
ground water.    The  worst-case  situation  of
complete containment system failure is unlikely to
occur, however,  because five-year reviews  (see
Section 3.4) are conducted at all sites where wastes
are managed onsite above concentration levels that
allow for unrestricted use and unlimited exposure.

2.2.2    EVALUATION OF SHORT-TERM
        HUMAN HEALTH RISKS FOR
        DETAILED ANALYSIS

    Short-term health risks generally include any
current baseline risks plus  any  new risks  that
would occur while implementing the remedy. As
discussed  previously,  the evaluation of potential
short-term risks involves the same general steps as
in the  baseline  risk assessment.   These steps,
however, generally will not be conducted in the
same level of detail for the FS.

    Other  important points concerning level of
effort should be emphasized here.  For example,
the  Resource  Conservation and  Recovery  Act
(RCRA)  has performance standards for many
commonly used CERCLA remedial technologies
(e.g., incineratiqn). The risks associated with many
of these technologies were analyzed in developing
these standards, and the standards were set such
that  the risks  associated with operation of the
technology would be  acceptable.   Therefore, a
detailed evaluation of the  risks associated  with
RCRA-regulated technologies generally would not
be necessary.  On the other hand, depending on
site-specific factors  such as the  toxicity  of  site
contaminants and the proximity of populations, a
more detailed evaluation of short-term risks may
indeed be appropriate.

    Detailed analyses may also be appropriate for
less-characterized  technologies (e.g., innovative
technologies).   In  addition, alternatives  with
multiple short-term releases or substantial baseline
risks  may  need a  more detailed  evaluation  to
determine whether cumulative risks are expected to
be within acceptable levels.

    Of  special note is that the short-term risk
evaluation  for remedial  alternatives  during  the
detailed analysis  includes  an evaluation  of  the
potential for short-term risks to two groups of
individuals:   (1) neighboring populations  (which
include  onsite  workers  not  associated with
remediation)  and  (2)  onsite workers associated
with remediation.

    Appendices A through D provide information
that  can  be  used  when  a more  quantitative
evaluation of short-term risks is needed to support
the  selection  of  a  remedy.    Chapter  8  of
RAGS/HHEM Part A also provides guidance  on
characterizing short-term risk.

    Evaluate  Short-term  Exposure.  A qualitative
exposure  assessment  for  remedial  alternatives
during the detailed analysis generally involves —
just as in the baseline risk assessment, but in a less
quantitative  manner — using the  concept  of
reasonable maximum exposure (RME) to evaluate
release sources, receiving media, fate and transport,
exposure points, exposure routes,  and receptors
associated with a particular alternative.
                                                -15-

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     An important difference between the baseline
 risk assessment and the risk evaluation of remedial
 alternatives involves exposure sources.  For the
 baseline risk assessment, the source of exposure is
 untreated  site contamination.   For  remedial
 alternatives, however,  the potential sources  of
 exposure are  the releases that  result from the
 implementation  of remedial  technologies.    In
 additipn,  some   remedial   alternatives    (e.g.,
 incineration, biodegradation) may result in new
 chemicals that were not previously assessed for the
 site.

    The first  step  of  the exposure assessment
 involves identifying the types of releases associated
 with  a particular waste  management approach.
 During  the   detailed   analysis, methods   for
 mitigating   potentially   significant  short-term
 releases should be examined, and releases that are
 expected to be most difficult to control should be
 highlighted.

    Appendices A and D of this guidance  each
 contain  two   matrices  that  should  assist  in
 characterizing the releases that may  occur during
 remedy implementation.  Exhibit A-l provides a
 brief description of common remedial technology
 processes, and  Exhibit A-2 summarizes potential
 releases  to different media during  the normal
 operation of various technologies.  Exhibit D-l
 provides a summary of releases associated  with
 radiation remedial technologies, and Exhibit D-2
 includes  a  qualitative estimate of the potential
Short-term  risks  posed by a radiation  remedial
 technology.

    After the releases and their receiving media
have been identified, the next step of the exposure
assessment is to determine whether major exposure
pathways   exist     Characterizing   site-specific
exposure pathways involves identifying:

 •   the  general   fate  and   transport  of  the
    contaminants  that  are  released  from  the
    technology (e.g., downwind transport);

 •   the potential exposure points and receptors
    (e.g., nearby downwind residents); and

 •   potential exposure routes (e.g., inhalation).

Exhibit 2-1 illustrates an example of an exposure
pathway for a remedial alternative. More detailed
information  concerning  exposure  pathways  is
available in Chapter 6 of RAGS/HHEM Part A.
 The flow charts contained in Exhibit 6-6 of Part A
 are  particularly   useful  in  determining   the
 populations potentially exposed by releases into a
 particular  medium.  Transfers of  contaminants
 from  one  medium  to other media also  are
 addressed.

     At  this  point,  a  quantitative  exposure
 assessment — if  needed  —  would involve  (in
 addition to identifying release sources, exposure
 routes, and exposure points):

 •   quantifying releases;

 •   evaluating environmental fate and transport;

 •   determining exposure  point  concentrations;
    and

 •   calculating intakes.

 All of these steps are discussed in Chapter 6 of
 RAGS/HHEM Part A.

    Throughout    the  short-term   exposure
 assessment, the assessor  must  continually  ask
 whether the potential exposure warrants the level
 of quantitation being used.  At times, the answer
 may not be known until the end  of  the exposure
 assessment. For example, if short-term exposure
 was estimated to  be very similar to long-term
 exposure, it would not  be necessary to  expend
 resources  to  obtain  the short-term   toxicity
 information needed to quantitatively characterize
 risk.

    A major  difference between the  exposure
 assessment conducted during  the baseline  risk
 assessment and the one conducted during the risk
 evaluation   of  remedial  alternatives  is   the
 evaluation  of the timing and duration of releases.
 Because a number of different activities will lake
 place during implementation, it is likely that  the
 quantities of hazardous substances released to  the
environment will vary over time. For example, as
seen in Exhibit 2-2, one remedy can have several
distinct phases, each  with .different  exposure
potentials.  It  may be important to determine  the
sequence of events and  likely activities at each
phase of the  remediation,  so  that the exposure
point can be evaluated for  each phase.  This will
also ensure that appropriate short-term exposure
durations are identified and that the  potential  for
releases to  occur simultaneously and thus result in
cumulative  risk   is  considered.   As  seen  in
                                                -16-

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                                         EXHIBIT 2-1

                           ILLUSTRATION OF AN EXPOSURE
                         PATHWAY FOR A REMEDIAL ACTION
 Exposure Medium
       (Air)

          Exposure
            Point
                             Transport Medium (Air)
Prevailing Wind Direction
                  Inhalation
                  Exposure Route
                                                                          Volatile Organic
                                                                          Compounds
                                                                                    round Water
                                                                                   Pump and Treat
                                                                                   Apparatus
                                                                                Contaminated
                                                                                Ground Water
Exhibit 2-2,  this  issue  is  complicated by  the
possible presence of baseline exposures.

    Appendix B provides references — organized
based on several important categories of remedial
technologies — that can be consulted to quantify
the  release  of  and   therefore  exposure  to
contaminants.  The information in Appendix B
includes  a brief discussion of considerations in
release modeling  and monitoring,  a list of key
technology-related parameters generally needed as
inputs for models (e.g., meteorological conditions,
operation    characteristics,    soil/media
characteristics), an  annotated  list of primary
references, and a list of additional references.

    Evaluate Short-term Toxicity.  The'releases
that  may occur  during implementation  of a
remedial alternative, and hence the exposure-point
                      concentrations, generally last for varying durations
                      and correspond to  less-than-lifetime exposures.
                      Consequently, any toxicity values used to evaluate
                      the risks  from these, shorter  exposures  must
                      correspond to the duration  of the release  (or
                      exposure). Three exposure durations, in addition
                      to  longer-term exposures, may be of concern at
                      CERCLA sites  undergoing remediation:  single
                      exposure events (minutes, hours, or single day),
                      very short-term exposures (up to two weeks), and
                      short-term exposures (two weeks to seven years).
                      Note  that  the  chronic  toxicity  values   for
                      noncarcinogenic effects used most frequently in the
                      baseline risk assessment may not be appropriate
                      without  modification for exposures of less than
                      seven years (otherwise they may be unnecessarily
                      conservative).
                                               -17-

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                                                       EXHIBIT 2-2

                ILLUSTRATION OF CUMULATIVE EXPOSURE FROM MULTIPLE RELEASES
00
              Exposure
                                                             Cumulative
                                                                                    Cumulative
                                                                                    Residual
                                                                                    Technology 1
                                                                                    Technology 2
                                                                                    Baseline (Uncontrolled)
                                                                                      Baseline (Uncontrolled)
                                                                                            Residual
                                                            Time

                         Note: The graph illustrates how nearby populations at some sites could be exposed to both residual risks
                              and risks from remediation technologies. The cumulative exposure illustrated is the sum of residual
                              exposure and exposures associated with releases from Technologies 1 and 2. This exhibit is for illustration
                              purposes only and is not meant to imply that this level of quantitation is neccesary or even desired.

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    Appendix C contains information concerning
the   use   of   short-term   toxicity   values.
RAGS/HHEM   Part   A  provides  additional
information on assessment of contaminant toxicity.
As discussed in Appendix C, the Supeirfund Health
Risk Technical Support Center CTSQ should  be
consulted in all  cases where short-term toxicity
values are needed.

    Characterize   Short-term  Risks  to  the
Community.     During  risk  characterization,
exposure  and  toxicity  information  is  brought
together to provide a measure or indication of the
magnitude and timing of short-term health risks  (if
any) from the remedial alternatives.  As discussed
previously,   risk   assessors   may   choose   to
characterize the short-term risks to the community
(i.e., persons who live or work in the vicinity of the
site) quantitatively for some sites and qualitatively
for others.    When  short-term  risks  are not
expected to  be a  problem  for  a  site, a  more
qualitative evaluation generally is appropriate.  In
these  cases,  a   qualitative  evaluation  of the
magnitude,  duration,  and/or  likelihood of the
exposures and risks should be  conducted, and
assessors  could  describe short-term  risks  in a
qualitative manner relative  to the results of the
baseline risk assessment.

    A quantitative evaluation of short-term risks is
most  likely  to be useful when  the  types, levels,
and/or  availability  of  hazardous  substances are
expected to change significantly  as a result  of
remediation.  If quantitative exposure estimates
and  toxicity data  are available, then  a  more
quantitative   risk   characterization   may    be
conducted.  The quantitative method that is used
to characterize these risks depends in part on the
toxicity  values that have been identified.  Some  of
these toxicity values (e.g., subchronic reference
doses) must be combined with the results of the
exposure assessment (i.e., intakes). The results  of
risk  characterizations  using this type of toxicity
value will be of the same type as those generated
in the baseline risk assessment:  hazard quotients
(or indices) or excess individual lifetime cancer
risks. If the toxicity values incorporate exposure
assumptions (e.g., as in one-  and ten-day health
advisories),  then  these values  are  compared with
exposure concentrations to determine whether the
risks are above  acceptable  levels.   Appendix  C
provides additional information  on  short-term
toxicity  values.
    Cumulative effects from multiple releases  or
multiple chemicals should also be considered, if
possible. If the risk characterization is qualitative,
then a discussion of the potential for cumulative
risks  from  multiple  chemicals and/or exposure
pathways    (e.g.,   due   to   simultaneous
implementation of several remedial technologies)
should be  provided.   If the results  of the risk
characterization are more quantitative (e.g., cancer
risks and hazard quotients), then the information
concerning duration and timing of releases can be
used to calculate the cumulative risks or  hazard
indices for  those releases that will occur at the
same time and affect the same populations.  If the
results of the quantitative risk characterization are
comparisons with short-term toxicity criteria, then
the total exposure concentrations can be calculated
for releases  that occur at the same time and affect
the .same  populations.   These  total  exposure
concentrations then can be compared to the short-
term  toxicity  criteria.     See  Chapter   8   of
RAGS/HHEM Part A for additional guidance on
characterizing short-term human health risks.

    Characterize Short-term Risks to Workers.
Worker health and safety issues should also be
considered during the development of the FS. The
Worker Protection Standards for Hazardous Waste
at 40 CFR 311 and 29 CFR 1910.120 establish
requirements for worker protection at CERCLA
sites,  including requirements for planning (i.e.,
health and safety plans, and emergency response
plans),   training,   and  medical   surveillance.
Although the standards encompass areas that are
not  directly  related   to   worker   risk
(e.g., illumination and sanitation), they also specify
requirements in areas that are directly relevant to
worker health risks. Specifically, once a remedy is
selected, the Worker Protection Standards require
that implementation of that remedy proceed with
the following risk-related considerations:

•   site characterization  and  analyses  prior to
    commencing remedial activities, specifically
    risk identification (see 29 CFR 1910.120(c));

•   proper  use of  engineering  controls,  work
    practices and personal"protective equipment
    (PPE) for employee protection (see 29 CFR
    1910.120(g)); and

•   preparation of emergency response plans that
    specify  how  the  site   employees  will  be
    protected   while   responding   to    onsite
                                                 -19-

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    emergencies that may occur  (see 29  CFR
    1910.120(1)).

It is important to note, however, that factors not
associated  directly with hazards particular to a
given site  (e.g., risk of accidents during  offsite
motor vehicle transport) are not usually considered
during the FS, but  instead  should be addressed
prior to remediation in the site  health and safety
plan.

    The exact nature of the assessment of worker
safety issues for a remedial alternative will vary
with  each site.  For many types of sites and
remedial alternatives, the risks to workers will be
well-characterized and will not  require  much
additional site-specific analysis.  These issues will
be  addressed  in more  detail in the  site-specific
health and safety  plan.   Thus,  a  qualitative
assessment of worker risk is appropriate for most
sites  during the FS and can be based on three
types of risk.

•   Potential for exposure to hazardous substances
    during onsite remedial  activities.  The most
    significant factor determining the potential for
    exposure to hazardous substances is the nature
    of the onsite contamination.  Because onsite
    remediation workers are equipped with  the
    appropriate PPE and  are  required  to  use
    appropriate engineering controls, their risk
    generally  should be minimal.   Factors that
    affect  the potential for exposure, however,
    include the likelihood  of PPE  failure.   In
    general, more restrictive PPE is more likely to
    fail  due  to  considerations such as  worker
    mobility   and  visibility    constraints,  and
    potential for worker heat stress.

 •    Potential for injury due to physical hazards.
     Onsite remediation workers may be exposed to
     hazards other  than  exposure to hazardous
     substances. Hazards such as  explosion, heat
     stress, and precarious work environments may
     also pose threats to workers.

 •    Potential  for   exposure  during emergency
     response activities (assuming  the need arises
     for  onsite emergency response). Part of the
    design  of  a  remedial  alternative  should
    consider  the. potential for worker  exposure
    during  emergency  responses  that  may be
    required in the event of remedy failure. For
    some remedial alternatives, it is possible that
    emergency assistance would be handled in part
    by onsite workers, with offsite assistance (e.g.,
    county HAZMAT teams) as required.

Alternatively,  it  is possible  that  an emergency
response plan would require the evacuation of
onsite remediation workers  and  use of offsite
emergency  responders.

2.3    CASE STUDIES

    The following  two  case  studies  provide
examples  of the  evaluations of  long-term  and
short-term  risks  that are  conducted during the
detailed analysis.  Both case studies present an
evaluation  of only one technology  for  one of
several  alternatives that are considered for the
hypothetical  site.  An actual  detailed analysis
would  include  a similar  evaluation for other
technologies  and alternatives as well.  The two
sites considered in the case studies are identical in
all  respects, except one:    the XYZ Co.  site
considered in  Case Study #1 is distant  from
residential  or worker populations,  while the ABC
Co. site considered in Case Study #1 is adjacent to
a residential  neighborhood. A more quantitative
analysis was conducted in Case Study #2 because
of concern for potential short-term  exposures to
the neighboring community.

    The sites presented in these case studies are
abandoned   industrial   facilities    that   are
contaminated  with  various   volatile   organic
compounds (VOCs)  and  heavy metals.   VOCs
contaminate both the soil and ground water at the
sites, while metals are found in the  soil only.  A
number of  leaking  drums  were stored above
ground at  the sites and were removed prior to the
RI.  There  are also  two  lagoons filled with
hazardous  sludges.  City ground-water wells  are
located approximately  1/4 mile from  the' sites.
VOCs  have  been detected in the wells at  levels
high enough to force the city to use an alternate
water source.
                                                 -20-

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                                           CASE STUDY #1:
                     QUALITATIVE EVALUATION DURING DETAILED ANALYSIS

 [Note:  This case study presents an evaluation of only one technology for only one of several remedial
 alternatives; an actual detailed analysis would address other technologies and alternatives as well.  All data in
 this case study are for illustration purposes only.]

 Remedial Alternatives

      Based on the, results of the development and screening of alternatives, the site engineers have identified five
 alternatives  (A through E) to be evaluated for use as remedies at the XYZ Co. site.  One of the technologies
 included in Alternative C is ground-water pumping and  air stripping for the VOCs in ground water.

 Evaluation of Long-term Risks

      Meeting PRGs for all contaminants in ground water is uncertain at this point due to the complex nature of
 the contaminated aquifer.  If after remedy implementation it is determined that Alternative C does not meet PRGs
 for all contaminants in ground water, then the residual  risk remaining after  implementation will be examined to
 determine whether other measures need to be taken to assure protectiveness. There are no residual risks for media
 other than ground water for the pump-and-treat/air stripping component of Alternative C.

 Evaluation of Short-term  Risks

      The time-frame for air stripping of VOCs from ground water at the XYZ Co. site — and therefore the time
 frame considered for evaluating short-term risks — is at  least 20 years, and possibly as many as 50, depending on
 factors such as the specific.aquifer characteristics.                                                     .

      Releases and Receiving Media.  The most likely release of concern from an air stripper is the release of air
contaminated with VOCs.  The type of air stripper being considered for the  XYZ Co. site generally achieves 99
percent  or better removal of VOCs from water.  The vapor phase VOCs contained in the air stripper off-gases then
can be removed if necessary using air pollution control devices such as granular activated carbon columns or an
afterburner, which generally achieve 90 to 99 percent destruction or removal of contaminants from the vapor phase.
However, there will still  be some small release of contaminants that may need to be examined further  during the
design stage of this remedy (if selected).  Also, air pollution control devices will produce residues that in turn may
need  to be treated. Other releases associated with air stripping include treated water containing residual organic
contaminants that will be released to surface water, and, possibly, fugitive air emissions due to leaky  valves and
fittings.

      Fate and Transport.  Exposure Points, and Exposure Routes.  The release of VOCs into the air during  air
stripping at  the XYZ Co.  site could result in inhalation of volatiles transported through the air.  However, the
nearest  target  population is over one mile from the site.  Long-term average concentrations may be a concern, as
well as shorter-term or peak concentrations that may occur under certain conditions (e.g., temperature inversions).

      Short-term Risks. The time period of exposure to air stripper off-gases (20 to 50 years) is a significant portion
of a human  lifetime.  However,  because the concentrations of VOCs in ground water are not unusually high, the
releases associated with the air stripper are well-characterized, and there is no nearby target population, quantitation
of these risks is not needed to select a preferred alternative.
                                                  -21-

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                                           CASE STUDY #2:
                    QUANTITATIVE EVALUATION DURING DETAILED ANALYSIS

 (Note:  This case  study presents  an evaluation  of only one technology for only one of several remedial
 alternatives; an actual detailed analysis would address other technologies and alternatives as well. All data in
 this case study are  for illustration purposes onlv.1

 Remedial Alternatives

     Based on the results of the development and screening of alternatives, the site engineers have identified five
 alternatives (A through E) to be evaluated for use as remedies at the ABC Co. site.  One of the technologies
 included in Alternative C is ground-water pumping and air stripping for the VOCs in ground water. [For this case
 study, only benzene  from the pump-and-treat component of the remedial alternative will be analyzed in detail. In
 an actual analysis, each contaminant of concern and  each component of the remedy may need to be analyzed in a
 similar fashion.]

 Evaluation of Long-term Risks

     The RI has shown that the organic contaminants in the ground water are adsorbed to the aquifer material and
 are also dissolved in the ground water. The remediation goal for benzene will be readily met in the treated water,
 which will subsequently be discharged into the nearby surface water. Remediation of the water remaining in the
 aquifer, however, is  much less certain.  The residual  concentration of benzene in this remaining water will depend
 on several factors, including'the adsorptive characteristics of benzene with the aquifer material, the specific pumping
 regimen, and the length of time that this technology  is implemented.  If, at a later stage (e.g., during the five-year
 review), it is determined that the contaminants are not being extracted at the desired levels, the pumping regimen
 may need  to be modified (or some other approach may be needed). At a minimum, the pumping of ground water
 is expected to be an effective barrier against further contaminant migration. Due to the uncertainty regarding the
 residual concentration of contaminants that may remain in ground water, the permanence of the pump-and-treat
 technology, in terms of future risks, is unknown at this time.

 Evaluation of Short-term Risks

     Short-term impacts due to air emissions from air stripping are expected to be the most significant risks from
 the pump-and-treat component of the remedy at ABC Co. site. [This case study does not consider fugitive emissions
 from sources "upstream" of the air stripper (e.g., separators, holding tanks, treatment tanks), although these sources
may have  been evaluated in an actual risk assessment.] In order to assess these risks during the detailed  analysis
stage, exposure concentrations from the ABC Co. site will be estimated by combining emissions modeling with
 dispersion modeling. Before proceeding with this analysis, the following steps were taken.
                                                                        *.
 •    An appropriate atmospheric fate and transport model, derived from the SCREEN model developed by EPA's
     Office of Air Quality and Planning Standards  was chosen.  (A more complete listing and comparison of
     atmospheric fate models is given in Table 3-2 of the Superfund Exposure Assessment Manual [EPA 1988e].)

 •    Required inputs for the atmospheric fate and  transport model were obtained.  These inputs included the
     emission rate of contaminants from the air stripper into the atmosphere (based on contaminant concentrations
     in ground water, system flow rate efficiency of the air stripping process, and efficiency of the air pollution
     control device);  atmospheric dispersion factors for contaminants; and meteorological data (wind speed, prevalent
     direction, stability,  mixing height, and temperature).  More detailed parameters, such as surface  roughness
     height and specific topographic features, were not required for the model that was chosen.

                                              (Continued)
                                                  -22-

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                                          CASE STUDY #2:
                    QUANTITATIVE EVALUATION.DURING DETAILED ANALYSIS
                                            .  (Continued)

•   The population that will be affected by short-term releases was identified. This information was obtained from
    the baseline risk assessment, and was based  on the population distribution and density of the surrounding
    community, and meteorological data such as  the prevailing wind direction.

•   The toxicity characteristics of the contaminants were obtained from the baseline risk assessment.

    Exposure Assessment.  Releases are expected to occur during both the construction and the implementation
stages of the pump-and-treat technology.  The time frame for each of these stages varies and, therefore, the release
and exposure potential also will vary. The most probable release of concern from implementation of the air stripper
[the focus of this case study] has been identified as the release of air contaminated with volatile organic chemicals
(VOCs) from the stripping tower to the atmosphere. Benzene is one of the volatile contaminants in the ground
water being treated, and is expected to be present as a residual in the stripper off-gases. The following equation
(EPA, Emission Factors for Superfand Remediation Technologies, Draft, Office  of Air  Quality Planning and
Standards, 1990) was used to calculate the benzene emission rate into the air stripper off-gases:

                  ER(g/s)  =   C x Qin x (SE/100) x K

       where    ER =   emission rate of benzene (g/s)
                 C   =   concentration of benzene in water = 2.5 mg/L
                 Qin =   influent water flow rate = 1700 L/min
                 SE =   stripping efficiency of  tower for benzene = 99.99%
                 K   =   constant to convert units = 1.67 x 10"5 (g-min/mg-s)

An SE of 99.99 percent is used in these calculations to determine the reasonable maximum emission rate of benzene
into the air.  Actual SEs would be between 90 and 99.99 percent, depending on several operating parameters.
Solving this equation, ER = 0.071 g/s.

    Because this system will use an air pollution control device (APCD) such as granular activated carbon (GAG)
columns to remove contaminants from gases released to the atmosphere, ER is the rate of release of benzene from
the ground water into the stripper off-gases rather than the rate of release of benzene directly to the atmosphere.
The release rate of benzene to the atmosphere, therefore, can be calculated using the following equation:

                 q = ER x (1 - DRE/100)

         where   q        =   mass release rate to atmosphere (g/s)
                 ER      =   emission rate from air stripper to APCD = 0.071 g/s
                 DRE    =   destruction/removal efficiency of APCD = 95%

A DRE of 95 percent is used to obtain a reasonable maximum  release rate to  the atmosphere. Applications of
similar APCDs achieve 95  to 98 percent destruction and  removal efficiency for benzene in air. Solving for the
atmospheric release rate of benzene, q = 0.0035 g/s.

    Using fate and transport modeling [analysis not shown], the atmospheric release rate of benzene is converted
to an  exposure point concentration at a residence  250 m downwind of the site.  The short-term air concentration
(24-hour average) of benzene is estimated to be 6 x 10'4 mg/m3. The average annual longer-term concentration of
benzene in air at the site boundary, as determined by the same model, is estimated to be 3.4 x 10"4 mg/m3.

                                              (Continued)
                                                  -23-

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                                           CASE STUDY #2:
                     QUANTITATIVE EVALUATION DURING DETAILED ANALYSIS
                                               (Continued)

     The only potential exposure pathway identified for releases from the air stripper is the air (inhalation) pathway.
Because the toxicity  criterion used  to  characterize short-term risk  is a threshold  concentration (see Toxicity
Assessment below), a short-term intake does not need  to be calculated.  The longer-term intake is needed to
evaluate the cancer risk associated with inhalation of benzene. This intake is calculated by first obtaining the long-
term site-specific exposure duration of 30 years from the baseline risk assessment. (An exposure duration of 30
years is used because, while the time for  implementation of the pump and air stripping technology may be up to 50
years, an individual is not expected to stay in the community for more than 30 years.  If the maximum time for
implementation were less than the exposure duration identified in the baseline risk assessment, then exposure would
be computed using the maximum implementation time as the exposure duration.)  Using other exposure values
obtained from the baseline risk assessment (e.g., inhalation rate of 20 m3/day), the longer-term (lifetime average)
intake of benzene due to the air stripper is approximately 7.3 x 10'5 mg/kg-day.

     These concentrations and intakes are based on conservative steady-state assumptions regarding atmospheric
conditions. Therefore, there is uncertainty surrounding the atmospheric data (which are inputs to the model)  that
could lead to higher (but probably lower) concentrations.  For example, variations in wind speed and direction will
result in different contaminant concentrations for both maximum  short-term and long-term exposure point
concentrations. Some amount of published research data is available (mainly from water treatment plant studies)
on the reliability of the APCDs used in air stripping. This information, combined with data from previous program
experience, indicates that the uncertainty associated with the  effectiveness of the APCDs is low.

     Toxicity Assessment. To assess risk from exposure to the short-term benzene concentration (24-hour average),
a toxicity criterion corresponding to a similar exposure duration is used.  One such criterion, identified through
consultation with the TSC, is EPA's acute inhalation criteria (AIC). The AIC provides a threshold level above which
acute inhalation exposure to benzene could result in toxicity to the most sensitive target organ (bone marrow and
the immune system).  The AIC for benzene is 190 ug/rn3:.  [In this case study, the AIC for benzene was assumed
to be readily available. In an actual risk  evaluation, this may not always be the case.  When toxicity information is
not readily available — especially when, as in this case study,  the longer-term exposure point concentration is not
significantly different from the shorter-term point concentration (and the longer-term has toxicity information)—then
either delaying the assessment or expending resources to obtain the shorter-term toxicity  information  is  not
recommended.]

     To assess risk from exposure to the longer-term benzene  concentration (annual average) for the 30-year
exposure duration, the inhalation cancer slope factor for benzene of  0.029 (mg/kg-day)'1 is identified from the
baseline risk assessment.

     Risk Characterization.  Short-term risk to  the community  from  benzene is determined by  comparing the
short-term concentration of 6 x 10^ mg/m3 (i.e., 0.6 ug/m3), with the AIC of 190 ug/m3, to result in a ratio of 0.003.
Because this ratio is less than 1, short-term risk to the community solely from benzene is considered to be unlikely.

     Using the longer-term intake of 7.3 x 10'5 mg/kg/day, and the slope factor of 0.029 (nig/kg/day)'1, the upper-
bound excess individual  lifetime cancer risk to  the community  from long-term exposure  to benzene in  the
atmospheric releases from the air stripper is approximately 2 x 10'*, within EPA's acceptable risk range.

     [Uncertainties associated with the site-specific exposure information and the toxicity information, discussed in
more detail in the baseline risk assessment, also  are important to consider at this stage of the analysis.]
                                                   -24-

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                                   CHAPTERS

                    RISK  EVALUATION AFTER
                     THE FEASIBILITY  STUDY
    After the FS is  completed, a  remedy is
 proposed, and, if selected, is documented in the
 ROD. Following this, the remedy is designed and
 implemented, and then deletion/five-year reviews of
 the site take place. This chapter discusses the role
 of risk information during these activities. Note.
 however, that not all of these risk evaluations nor
 a significant level of quantitation may be needed
 for every site.  The guiding principle is that risk
 evaluations after the FS should be conducted as
 necessary to ensure that the remedy is protective.

 3.1   RISK EVALUATION FOR
       THE PROPOSED PLAN

    The purpose of a risk evaluation during the
 proposed plan stage is to refine previous analyses
 conducted during the  FS,  as  needed.   If new
 information becomes available during the public
 comment period for the proposed plan, additional
 analysis of  the  alternatives may need  to be
 conducted at this time.  If additional analysis is
 conducted, it should be  conducted for all the
 alternatives, as appropriate, and not just for the
 preferred alternative.


 3.2   DOCUMENTATION OF
       RISKS  IN THE ROD

    Several  risk-related  analyses  should  be
 documented  in  the  ROD.   The comparative
 analysis section should include a discussion of risk
 as it pertains to  the three risk-related criteria:
 long-term effectiveness, short-term effectiveness,
 and overall protection of  human health and the
 environment. The discussion of overall protection
 of  human health  and  the environment should
 include a  discussion of  how the remedy  will
 eliminate, reduce, or control the risks identified in
 the baseline risk assessment and whether exposure
will be  reduced  to acceptable  levels.    The
discussion   of   long-term  effectiveness   (and
 permanence) should address, where appropriate,
 the residual risk from untreated waste remaining at
 the site. The part of the decision summary that
 focuses on the selected remedy should present:

 •  the chemical-specific remediation levels to be
    attained at  the conclusion of the response
    action;

 •  the corresponding chemical-specific risk levels;

 •  the points (or areas) of compliance for  the
    media being addressed; and

 •  the lead agency's basis for the remediation
    levels (e.g., risk calculation, ARARs).

 In addition, the ROD should indicate whether  the
 site will require five-year reviews (see Section 3.4).
 In  some cases, additional risk information (e.g.,
 anticipated  post-remedy cumulative risk for  an
 environmental medium or for a site) may need to
 be included in the ROD.

    Interim Final Guidance on Preparing Superfund
Decision Documents  (EPA  1989f), Role of  the
Baseline Risk Assessment in Superfund Remedy
Selection   Decisions   (EPA   1991d),  and
RAGS/HHEM  Part   B   provide  additional
information on documenting risks in the ROD.

3.3   RISK EVALUATION DURING
       REMEDIAL  DESIGN/
       REMEDIAL ACTION

    The activities  during remedy design and
implementation that may involve consideration of
risk include refining risk  evaluations  during
remedial  design,  monitoring  short-term  risks,
evaluating attainment of remedial  levels in the
ROD, and evaluating residual risk.
                                           -25-

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3.3.1    RISK EVALUATION DURING
        REMEDIAL DESIGN

    The process of evaluating long-term and short-
term risks, which began during the FS and may
have  continued  during  development  of  the
proposed plan, also may continue during design of
the selected remedy for some sites.  The purpose
for risk evaluations during the  remedial design is
to  ensure that  the  selected  remedy  will be
protective. These evaluations can be conducted by:
(1) refining previous analyses,  as needed, and/or
(2) identifying the need for engineering controls or
other measures to mitigate  risks.   Methods for
evaluating long-term  and short-term risks  are
discussed in more detail in Chapter 2.

3.3.2    MONITORING SHORT-TERM
       HEALTH RISKS DURING
        IMPLEMENTATION

    If the potential for short-term health effects
due to  releases during remedy implementation
needs to be assessed (e.g., due to high uncertainty
concerning predicted   risks  to communities  or
remediation workers), a sampling  and  analysis
strategy   to   accurately  determine   exposure
concentrations should be developed.  This strategy
may need  to consider the following elements:

•   location of sampling;

•   sample collection and handling procedures;

•   chemicals to be monitored and methods used;
    and

•   statistical considerations regarding the analysis
    of results.

The monitored exposure concentrations should be
compared to  short-term health-based benchmarks
(see Appendix C) to help in  determining whether
the release presents a  threat  to human health.

33,3    ASSESSING ATTAINMENT OF
        SELECTED REMEDIATION LEVELS
        DURING IMPLEMENTATION

    The RPM, risk assessor,  and others should be
involved in developing a sampling and analysis
plan to measure whether the selected remedy has
attained the remediation levels in the ROD. As in
the baseline  risk assessment,  this sampling and
analysis should provide data that can be used to
develop RME estimates. This plan is site-specific
and  may  need to consider the same  elements
presented in  Section  3.3.2,  plus the  relevant
remediation levels for the chemicals of concern.

    The plan for  measuring attainment should
ensure   that  sufficient   data   to    evaluate
protectiveness of human health will be  available.
For example, at a minimum, those chemicals that
contribute to major portions of the site risk should
be selected for measuring attainment.   The two-
volume set Statistical Methods for Evaluating the
Attainment of Cleanup Standards (EPA 1988d)
outlines a number of statistical methods that can
be used to measure attainment. EPA is developing
additional guidance on this topic.

3.3.4    EVALUATION OF RESIDUAL  RISK

    This step —  which  may be conducted  at
completion of the remedy and perhaps during a
five-year review (see next section) — may  be
needed to ensure  that  the remedy is protective.
This step may be different from the assessment of
attainment of remediation  levels selected in the
ROD because it may more closely  consider the
expected land use and cumulative effects (e.g., due
to multiple  chemicals or exposure pathways).
Residual risk estimates can be conducted at any
time after the remedy  has commenced until the
end of the remedy. Typically, a final evaluation of
the cumulative site risk may be done  following
completion of the final operable unit to ensure
that residual risks from  multiple contaminants,
pathways, and operable units that affect the same
individuals are at protective levels.

    In  general,  the same equations,  exposure
parameters, and toxicity values that were used to
determine the baseline risk for a site can be used
to assess the final clean-up  (risk)  level that a
remedy has achieved. The concentrations that are
used to calculate these risks, however, are the final
measured concentrations of the contaminants that
remain at the site, not the remediation levels in
the ROD.   The  following are other  potential
differences between the baseline risk assessment
and evaluation of residual risks.

 •   Significant levels of "new" chemicals (e.g., that
    were  not identified during the  baseline risk
    assessment but that may have resulted from
    the remedy or were not discovered until after
    remedy implementation) should be considered
    in evaluating residual risk.
                                               -26-

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•   Changes in land use since the time of the
    baseline risk assessment may require changes
    in  exposure parameters  (e.g.,  contact rates,
    exposure frequency and duration).

•   Toxicity values may have been updated since
    the baseline risk assessment.  The most recent
    toxicity values in IRIS and HEAST should be
    used in calculating  residual risk.

    For  some  sites  where   engineering  or
institutional controls rather than treatment-based
remedies are  employed,  the  concentrations of
chemicals in a contaminated medium may remain
the same as the baseline concentrations.  The risk
will have been reduced  or eliminated, however, by
mitigation or elimination of the exposure pathway
(e.g., by mitigating direct contact with soil by using
a  cap  or institutional controls, or eliminating
ingestion  of  contaminated  drinking water by
providing an alternate  water supply).  These risk
reductions  and associated exposure assumptions
should be clearly presented.

3.4    RISK EVALUATION DURING
        FIVE-YEAR REVIEWS

    Section 121(c)  of CERCLA  provides  for
reviews  of  remedies  that result in hazardous
substances remaining at the site no less often than
every five years after the initiation of the remedies.
The purpose of the reviews is to assure that human
health and the environment are being protected by
the remedial alternative that was implemented.

    The remainder of this section briefly describes
the purpose of five-year reviews, the sites for which
five-year reviews are  conducted,  and the  risk-
related activities that  may be conducted during
five-year  reviews.     More   detailed  guidance
regarding five-year reviews is available in Structure
and Components of Five-year Reviews (EPA 1991e).

3.4.1   PURPOSE OF FIVE-YEAR REVIEWS

    A five-year review  is intended to ensure that a
 remedy remains protective of human health and
 the environment.   The more specific goals of a
 five-year f eview are:

 •   to confirm that the remedy (including any
     engineering or institutional controls) remains
     operational and functional; and
•   to evaluate whether clean-up standards (based
    on risk or ARARs) are still protective.

The first goal may be  accomplished primarily
through a review of the operation and maintenance
records for  a site and through a site visit and
limited  analysis.  The second  goal  includes an
analysis  of  requirements  that  have  been
promulgated by the federal or state governments
since ROD  signature to  determine whether they
are ARARs and whether they call into question
the protectiveness of a remedy.

    In  addition  to  considering ARARs  for
substances designated as contaminants of concern
in the ROD, the reviews may include changes in
ARARs for  substances  not  addressed under
contaminants of concern.    Where  remediation
levels in the ROD were based on risk calculations
(rather than ARARs), then  new information —
such  as  revised  toxicity  values or  exposure
parameters   —  that   could   influence   the
.protectiveness of the remedy should be considered.
Based on this analysis, the reviewer can determine
whether the original remediation levels set out in
the ROD are still protective.

3.4.2   SITES THAT RECEIVE FIVE-YEAR
        REVIEWS

    Two types of five-year reviews are conducted:
statutory and policy.   . Statutory  reviews  are
conducted   for   remedies  selected   after  the
enactment of SARA where,  after the remedy is
complete, hazardous substances are present above
levels that allow for unlimited use and unrestricted
exposure. These sites generally include:  (1) sites
with  remedies  requiring  access  or   land-use
restrictions  or controls (i.e., remedies that achieve
protectiveness through the use of engineering or
institutional controls); and (2) sites with remedies
that achieve protectiveness for the current use, but
include restrictions on activities due to limits on
exposure (i.e., sites cleaned up to levels that would
be protective for a nonresidential land use, but
would not be protective for residential or other
 land use).   Policy reviews are conducted for: (1)
 sites with long-term remedial actions (LTRAs) or
 other remedies that require five years or longer to
 achieve levels that  would allow for unlimited use
 and  unrestricted  exposure  and (2)  remedies
 selected before the enactment of SARA where
 hazardous substances are present above levels that
 allow for unlimited use and unrestricted exposure.
                                                -27-

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    Statutory reviews may be discontinued only if
levels of hazardous substances fall permanently to
a  point that  would allow  unlimited  use  and
unrestricted exposure.  Policy reviews for LTRAs
should be discontinued when the remediation goals
specified in the ROD are achieved, assuming these
levels allow for unlimited use and unrestricted
exposure.  Achievement of these levels must be
verified by an appropriate period of monitoring.

3.4.3    RISK-RELATED ACTIVITIES DURING
        FIVE-YEAR REVIEWS

    Three levels of effort have been defined for
five-year reviews.  The following are risk-related
activities conducted for the three levels.

•   At Level I, the reviewer will consider the risk
    assessment information contained in the ROD
    and ROD  summary.

•   At  Level  II,  the reviewer will conduct  a
    recalculation  of  the  original baseline  risk
    assessment using information obtained during
    the review  (e.g.,  new  toxicity  data).   If
    appropriate, additional data may be collected.
    Ongoing monitoring may provide such data.
•   At Level III, the reviewer will reevaluate the
    risk assessment, and, if appropriate, conduct a
    new risk assessment. Such an assessment may
    be appropriate in order to address a new site
    condition, such as a new exposure pathway.
    New data may be collected as necessary for the
    risk assessment.  If possible, however, existing
    data should be used.

    The appropriate level of review depends on
site-specific conditions and the confidence level for
the selected remedy.  The proposed level of the
first review is to be included in the ROD. A Level
I review should  be appropriate  in all but a  few
cases  where  site-specific circumstances  suggest
another level either at the outset of the review or
because findings of the review suggest the need for
further analysis.  A Level III review would not be
proposed in the ROD, but would be initiated in
response  to   specific   concerns  regarding  the
performance of the remedy or the risks at the site.
The level of effort, particularly  for  subsequent
reviews, also depends on the initial findings of the
review.  Structure  and  Components  of Five-year
Reviews   (EPA   1991e)   provides   additional
information concerning the appropriate level for
reviews and the activities that are conducted at
each level.
                                                -28-

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                                 REFERENCES
U.S. Environmental Protection Agency (EPA). 1988a. Community Relations in Superfund: A Handbook.
Interim Version. Office of Emergency and Remedial Response. EPA/540/6-88/002 (OSWER Directive
9230.0-3B).

EPA. 1988b. Guidance on Remedial Actions for Contaminated Ground Water at Superfund Sites. Interim
Final. Office of Emergency and Remedial Response.  EPA/540/G-88/003 (OSWER Directive 9283.1-2).

EPA 1988c. Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA,
Interim Final.  Office of Emergency and Remedial Response.  EPA/540/G-89/004 (OSWER Directive
9355.3-01).

EPA 1988d. Statistical Methods for Evaluating the Attainment of Superfund Cleanup Standards  Volume I:
Soils and Soil Media.  Office of Policy, Planning, and Evaluation.  EPA 230/02-89-042.
                                             ~*
EPA 1988e. Superfund Exposure Assessment Manual.  Office of Emergency and Remedial Response.
EPA/540/1-88/001 (OSWER Directive 9285.5-1).

EPA. 1988f.  Seven Cardinal Rules of Risk Communication. Office of Public Liason. OPA-87-020.

EPA 1989a. Considerations in Ground Water Remediation at Superfund Sites.  Office of Emergency and
Remedial Response. OSWER Directive 9355.4-03.

EPA 1989b., Ecological Assessment of Hazardous Waste Sites: A Field and Laboratory Reference.
Environmental Research Laboratory.  EPA/600/3-89/013.

EPA 1989c.  Estimation of Air Emissions from Clean-up Activities at Superfund Sites. Office of Air Quality
Planning  and Standards. EPA-450/1-89-003.

EPA 1989d. Exposure Factors Handbook. Office of Health and Environmental Assessment. EPA/600/8-
89/043.

EPA. 1989e.  Interim Guidance for Soil Ihgestion Rates.  Office of Solid Waste and Emergency Response.
OSWER  Directive 9850.4.

EPA 1989f. Interim Final Guidance on Preparing Superfund Decision Documents. Office of Emergency
and Remedial Response.  OSWER Directive 9335.3-02.

EPA. 1989g.  Risk Assessment Guidance for Superfund: Volume I — Human Health Evaluation Manual
(Part A, Baseline Risk Assessment). Interim Final. Office of Emergency and Remedial Response.
EPA/540/1-89/002.

EPA 1989h. Risk Assessment Guidance for Superfund: Volume II — Environmental Evaluation  Manual.
Interim Final.  Office of Emergency and Remedial Response.  EPA/540/1-89/001A (OSWER Directive
9285.7-01).

EPA 1990a.  Guidance for Data Useability in Risk Assessment.  Office of Solid Waste and Emergency
Response. EPA/540/G-90/008 (OSWER Directive 9285.7-05).

EPA. 1990b.  Guidance on Remedial Actions for Superfund Sites with PCB Contamination. Office of
Emergency and Remedial Response.  EPA/540/G-90/007 (OSWER Directive 9355.4-01).
                                             -29-

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EPA. 1991a. Conducting Remedial Investigations/Feasibility Studies for CERCLA Municipal Landfill Sites.
Office of Emergency and Remedial Response. EPA/540/P-91/001 (OSWER Directive 9355.3-11).

EPA. 1991b. Risk Assessment Guidance for Superfimd, Volume 1, Human Health Evaluation Manual,
Supplemental Guidance: "Standard Default Exposure Factors".  Office of Emergency and Remedial
Response. OSWER Directive 9285.6-03.

EPA. 1991C. Risk Assessment Guidance for Superfund: Volume I — Human Health Evaluation Manual
(Part B, Development of Risk-based Preliminary Remediation Goals). Interim.  Office of Emergency and
Remedial Response. OSWER Directive 9285.7-01B.

EPA. 1991d. Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions.  Office of
Solid Waste and Emergency Response. OSWER Directive 9355.0-30.

EPA. 1991e. Structure and Components of Five-year Reviews.  Office of Emergency and Remedial
Response. OSWER Directive 9355.7-02.

EPA 1991f. Guidance on Oversight of Potentially Responsible Party Remedial Investigations and Feasibility
Studies. Office of Solid Waste and Emergency Response.  EPA/540/G-91/010a (OSWER Directive
9835.1(c)).
                                              -30-

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                               APPENDIX A
   SELECTED REMEDIATION TECHNOLOGffiS
    AND ASSOCIATED POTENTIAL RELEASES
    This appendix contains two exhibits designed
to assist during the FS in identifying some of the
potential  releases  that are associated  with
commonly used remediation technologies. Exhibit
A-l briefly describes each of the process options of
each technology in Exhibit A-2.  Exhibit A-2
summarizes several potential releases to air  or
water of common remedial technologies.  Process
variations for which potential releases are similar
are combined  under  the technology category.
Potential releases to surface water or ground water
are included in the  "water" column.   "Other"
releases include treatment residuals that need
further  treatment or  proper disposal.  In most
cases, this column refers to sludge or solid residues
that may also be hazardous.

   Risk  Reduction   Engineering Laboratory
(RREL;  Cincinnati, Ohio) plans  and conducts
engineering, research, and development related to
treatment of solid and hazardous wastes. RREL
personnel,provide site-specific technical services
involving specific  treatment  technologies and
CERCLA response processes including:

•  analysis of treatment alternatives,
•  treatability studies,
•  remedial design review,
•  construction QA/QC methods, and
•  contaminant source control and geotechnical
   test methods.

Regional EPA CERCLA  staff should  direct
questions regarding  evaluations of remediation
technologies, previous experience with remediation
technologies,  and  releases  associated   with
remediation technologies to the Engineering and
Treatment Technical Support Center,  RREL at
FTS 684-7406 or 513-569-7406.
                                       -31-

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                                            EXHIBIT A-l
                              REMEDIATION TECHNOLOGY DESCRIPTIONS
to
Technologies
Description of Process
SOIL AND SLUDGE
Soil Handling
Soil Excavation, Transport,
Dumping, and Grading
These processes use mechanized equipment to move contaminated soil. For some
treatment techniques, soil must be removed from a contaminated site and be transported
for treatment. Soil is then returned and replaced at either the original excavation or
another disposal site. Grading is a technique which can reduce infiltration into
contaminated soils and can also control runoff.
Thermal Destruction These are destruction processes which control temperature and oxygen availability, and
convert hazardous materials to carbon dioxide, water, and other products of combustion.
Circulating Bed Incineration
Rotary Kiln Incineration
Fluidized Bed Incineration
Infrared Incineration
Pyrolysis
Wastes and auxiliary fuel are introduced into the combustion chamber. Air is forced up
through the chamber from the bottom to promote mixing and complete combustion.
Particulate and gaseous products of combustion exit from the top of the combustion
chamber for treatment and disposal.
The combustion chamber is a rotating, inclined cylinder which mixes combusting materials
as it rotates. Wastes are fed into the chamber at the high end, along with air and auxiliary
fuel. Exhaust gases are treated and released, and ash residue is collected on the low end of
the kiln.
A bed of inert particles (e.g., sand) lies at the bottom of the cylindrical combustion
chamber. Air is forced up through the bed and the particles are fluidized (i.e., the particles
"float" in the airstream). Wastes and fuel are injected at the top of the chamber, into the
fluidized mass, where the mixture combusts. The turbulent atmosphere in the chamber
provides good mixing of wastes to ensure complete combustion and efficient heat transfer.
Waste.materials are fed into the furnace on a conveyor belt, and pass through on a wire
mesh belt. Heating elements provide infrared energy, oxidizing the materials. Waste gases
are passed through a secondary combustion chamber; ash exits on the conveyor.
Organics are slowly volatilized at lower temperatures than incineration processes. Waste is
fed into the primary combustion chamber and thermally treated without sufficient oxygen to
completely combust. Volatilized organics pass to a secondary chamber and are incinerated.
Solid residues from the primary chamber receive other treatment.
                                              (Continued)

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                                         EXHIBIT A-l (Continued)



                                REMEDIATION TECHNOLOGY DESCRIPTIONS
OJ
Technologies
Wet Air Oxidation
Aqueous Thermal Decomposition
Description of Process
The high temperature and high pressure properties of water are utilized in destroying
wastes. Contaminated solutions are treated at high temperatures (>600° C) and pressures
(3400 psi to 3700 psi). Contaminants are oxidized to simple organic compounds as large
amounts of oxygen are dissolved in solution.
Aqueous thermal decomposition works on the same principles as wet air oxidation, without
the addition of excess oxygen. •
Dechlorination
Glycolate Dechlorination
Using a specific solvent, chlorine atom(s) are removed from chlorinated hazardous
materials, and toxic compounds are converted to less toxic, more water-soluble compounds.
Reaction products are more easily removed from soil and more easily treated.
Biological Treatment
Composting
In-situ Biodegradation
Slurry-phase Biodegradation
Solid-phase Biodegradation
Contaminated material is mixed with bulking agents (e.g., sawdust, wood chips) and placed
in reactor vessels or piles. Aeration, temperature, and nutrient levels are controlled to
encourage microbial growth. Microorganisms then metabolize contaminants, breaking them
down into less-harmful materials.
Microorganisms are encouraged to decompose contaminants in soil without excavating the
soil and placing it in a controlled reactor. Nutrients, oxygen, and other necessary materials
can be injected into the contaminated area.
The wastes are mixed with water to achieve an aqueous mixture. The mixture is then
treated in a bioreactor, where it is mixed continuously to contact microorganisms and
contaminants. The bioreactor serves as a controlled environment for contaminant
degradation.
Soils are excavated and treated above ground so that treatment conditions can be closely
monitored iand adjusted to conditions that are ideal for biodegradation. Materials are
treated in a prepared area which can include volatile emissions collection and leachate
collection.
                                               (Continued)

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I
                                                                              EXHIBIT A-l (Continued)

                                                              REMEDIATION TECHNOLOGY DESCRIPTIONS
                                              Technologic
                                                                                                      Description of Process
                                   Vacuum/Vapor Extraction, Thermal Pesorption
                                      Low Temperature Thermal
                                      Stripping
Air, pressure, heat, and/or mechanical agitation provides a driving force for volatilizing and
removing contaminants from soil into an airstream for further treatment.  Separating
contaminants from soil simplifies the final treatment of contaminants	
                                      In-situ Vacuum/Steam Extraction
VOCs are removed from soil by applying a vacuum to wells that are placed in the
contaminated soil. VOC vapors are collected and treated above ground. Some systems also
inject hot air or steam into contaminated zones, raising temperatures and volatilizing organic
chemicals.
                                    Chemical Extraction & Soil Washing
                                      In-situ Chemical Treatment
Treatment chemicals are applied directly to contaminated soil.  A variety of compounds can
be applied, including neutralizing agents, oxidants, solidification/stabilization agents, and
nutrients for biological treatment.                    	
                                      Chemical Extraction & Soil
                                      Washing
Contaminants are washed from the excavated soil into a chemical solvent. The liquid is
treated to remove and destroy contaminants, and the solvent is reused.    	
                                      In-situ Soil Flushing
Inorganic or organic contaminants are extracted from soil by washing the soil with solvents.
Solvents are recovered, contaminants are extracted, and the solvents are recirculated
through the soils.              ^	
                                    Immobilization
                                      Capping
 Contaminated soil is covered with low-permeability layers of synthetic textiles or clay. The
 cap is designed to limit infiltration of precipitation and thus prevent migration of
 contaminants away from the site and into ground water.	
                                      Solidification/Stabilization
 Wastes are converted to chemically stable forms or are bound in a stable matrix.  Chemical
 reactions are utilized to transform hazardous materials into new, non-hazardous materials.
 The goal is to prevent migration of contaminants.	
                                      In-situ Vitrification
 Electrodes are placed vertically into the contaminated soil region, and an electrical current is
 applied.  The soil is melted by the resulting high temperatures.  When the melt cools and
 solidifies, the resulting material is stable and glass-like, with contaminants bound in the solid.
                                                                                         (Continued)

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                                          EXHIBIT A-l (Continued)



                                REMEDIATION TECHNOLOGY DESCRIPTIONS
w
en
; Technologies
Description of Process
GROUND AND SURFACE WATER
Natural Attenuation
Aeration/Air Stripping
Filtration
Sedimentation
Granular Activated Carbon (GAC)
Adsorption
Ion Exchange
Chemical Treatment
Biological Treatment
Contaminants in an aquifer disperse and dilute through natural ground-water transport.
Some natural degradation may occur.
Contaminants, usually volatile organic compounds, are transferred from liquid phase to
gaseous phase. By contacting contaminated water with clean air, dissolved VOCs are
transferred to the airstream to create equilibrium between the phases. The process takes
place in a cylindrical tower packed with inert material which allows sufficient 'air/water
contact to remove volatiles from water. Contaminants are then removed from the
airstream.
Filtration removes suspended solids from liquids by passing the mixture through a porous
medium.
Solids that are more dense than liquid settle by gravity and can be removed from the liquid.
Chemicals to aid settling maybe added. Settled solids result in a sludge which may be
treated further.
GAC is packed in vertical columns, and contaminated water flows through it by gravity.
GAC has a high surface area to volume ratio, and many compounds readily bond to the
carbon surfaces. Contaminants from water are thus adsorbed to the carbon, and effluent
water has a lower contaminant concentration. Water may be passed through several of
these columns to complete contaminant removal. Spent carbon (i.e., carbon trial has
reached its maximum adsorption capacity) is regenerated by incineration.
As contaminated water flows through the reactor vessel, ions of contaminants are adsorbed
to a synthetic resin in the vessel. The resin attracts and adsorbs contaminant ions, while
releasing non-harmful ions into the treated water.
Chemicals can be added to contaminated waters to chemically change or to remove
constituents. Precipitation can be accomplished through pH control; solutions can be
neutralized; contaminants can be oxidized; and solids can be settled out of solution.
Microorganisms in controlled-environment reactors are utilized to decompose contaminants
in water. Nutrients, pH, temperature, and oxygen availability are controlled. The organisms
degrade contaminants into simpler, safer compounds.
                                                (Continued)

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         EXHIBIT A-l (Continued)
REMEDIATION TECHNOLOGY DESCRIPTIONS
Technologies
Description of Process
Membrane Separation
Reverse Osmosis
Elecirodialysis
A semi-permeable membrane is used lo separate dissolved contaminants from liquids. High
pressure is applied to the contaminated solution, which drives only the liquid through the
membrane. The result is a highly concentrated contaminated solution on the high pressure
side of the membrane, and a purified liquid on the opposite side of the membrane.
This process concentrates ionic species that arc in aqueous solution. The solution is passed
through alternate cation-permeable and anion-pcrmeablc membranes that have an applied
electric polcntial. This potential provides a driving force for ion migration.

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                            EXHIBIT A-2
REMEDIATION TECHNOLOGIES AND SOME POTENTIALLY SIGNIFICANT RELEASES
Technologies
Air
Water"
Otherb
SOIL AND SLUDGE TECHNOLOGIES
Soil Handling
Soil Excavation, Transport,
Dumping, Screening and
Grading
• Fugitive emissions of
particulates and volatiles
• Runoff or leaching of
contaminants to surface or
ground water
• ' Seepage or runoff to nearby
soil
Thermal Destruction
Incineration: Rotary Kiln,
Fluidized Bed, Circulating
Bed, and Infrared
Pyrolysis ,
Wet Air Oxidation
Aqueous Thermal
Decomposition
• Fugitive and stack emissions
of metal fumes; particulates,
including metals and salts;
and products of incomplete
combustion, including organic
compounds, acid gases, CO,
NOX, and SOX
• Fugitive and stack emissions
of metal fumes; particulates,
including metals and salts;
and products of incomplete
combustion, including organic
compounds, acid gases, CO,
NO,,, and SOX
• Fugitive emissions of volatile
organic compounds
• Fugitive emissions of volatile
organic compounds
• Discharge of scrubber liquor
and blowdown
• Discharge of scrubber liquor
and blowdown
• Discharge of metals and
unoxidized organics
« Discharge of metals and
unoxidized organics
• Disposal of ash and other
solid residues
• Disposal of ash and other
solid residues
• Disposal of sludge residues
• Disposal of sludge residues
                              (Continued)

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r
       OJ
                                              EXHIBIT A-2 (Continued)
                      REMEDIATION TECHNOLOGIES AND SOME POTENTIALLY SIGNIFICANT RELEASES
Technologies
Air
Water1
Other1
Dechlorination
Glycolate Dechlorination
• Fugitive emissions of volatile
organic compounds
• Discharge of spent solvents
and degraded contaminants
to surface water, or leaching
to ground water

Biological Treatment
Composting
In-situ Biodegradation
Slurry-phase or Solid-phase
Biodegradation
• Fugitive emissions of
particulates and volatile
organics
• Fugitive emissions of volatile
organics
• Fugitive emissions of volatile
organics
• Leaching of metals and/or
organics
• Leaching of metals and/or
organics
« Discharge of treated water
• Discharge of non-degraded
byproducts in slurry liquor
and treated effluent
• Runoff to surface water or to
ground water (with solid-
phase process)


• Disposal of residual biomass
which may contain
hazardous metals and
refractory organics
Vacuum/Vapor Extraction, Thermal Desorption
Low Temperature Thermal
Stripping
In-situ Vacuum/Steam
Extraction
• Stack emissions of volatile
organics
• Fugitive emissions of volatile
organics
• Fugitive emissions of volatile
organics
• Discharge of scrubber
blowdown
• Discharge of contaminant
condensate
• Discharge of contaminant or
water condensate

• Disposal or regeneration of
spent activated carbon
                                                     (Continued)

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U)
VO
                                        EXHIBIT A-2 (Continued)

                REMEDIATION TECHNOLOGIES AND SOME POTENTIALLY SIGNIFICANT RELEASES
Technologies •
Air
Water"
Other*
Chemical Extraction & Soil Washing
In-situ Chemical Treatment
Chemical or Solvent
Extraction
Soil Washing
In-situ Soil Flushing
• Fugitive emissions of volatile
organic compounds
• Fugitive emissions of volatile
organic compounds
• Fugitive emissions of volatile
organic compounds
-\ '
• Fugitive emissions of volatile
organic compounds
• Runoff of uncontained
treatment chemicals
• Post-extraction discharge of
wastewater with extracted
contaminants
• Post-washing discharge of
wastewater with extracted
contaminants
• Leaching of contaminated
flush water, acids, bases,
chelating agents, or
surfactants
• Possible solvent residuals in
treated soil
• Possible solvent residuals in
treated soil
• Discharge of foam with
metals and organics
• Deposition of sedimentation
sludge residuals
• Deposition of untreated,
contaminated fines

Immobilization
Capping
Solidification/Stabilization
• Fugitive emissions of
particulates and volatiles
during cap construction
• Fugitive emissions of
particulates and volatiles
• Leaching of contaminants to
ground water
• None likely
• Lateral movement of volatile
organic compounds after
capping
• Potential leaching to soils
and ground water of
contaminants from deposited
material over time
                                              (Continued)

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i.
c
                                        EXHIBIT A-2 (Continued)



               REMEDIATION TECHNOLOGIES AND SOME POTENTIALLY SIGNIFICANT RELEASES
Technologies
In-silu Vitrification
Air
• Surface fugitive emissions of
volatile organics and volatile
metals during the process
Water*
• Discharge of scrubber
solution
• Possible contamination of
ground water under the
treatment area
Other*
• Potential lateral migration of
vaporized or leached
contaminants into the soil
that surrounds the vitrified
monolith
GROUNDWATER AND SURFACE WATER TECHNOLOGIES
Non-Treatment Actions
Natural Attenuation
Pump without Treatment
Air Stripping
Filtration/Settling
Granular Activated Carbon
Adsorption
• Emissions of volatile organic
compounds
• Emissions of volatile organic
compounds
• Stack and fugitive emissions
of volatile organics
• Fugitive emissions of volatile
organic compounds from
settling basin
• None likely
• Aquifer discharge to surface
water "
• Continued aquifer transport
of contaminants
• Discharge of untreated water
to surface water or Publicly
Owned Treatment Works
(POTW)
• Seepage of untreated water
• Discharge to surface water of
effluent treated water with
residual metals, particulates, ,
or nonvolatile organics
• Discharge of effluent water
containing dissolved solids or
unremoved particles
• Discharge of effluent with
non-adsorbable, low
molecular weight compounds

• Disposal of sludge residuals
from POTW
• Disposal of backwash or
cleaning residues
• Disposal of filter cake or
sludge containing organics,
metals, or other inorganics
• Disposal and/or regeneration
of spent carbon
                                              (Continued)

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                                                  EXHIBIT A-2 (Continued)

                REMEDIATION TECHNOLOGIES AND SOME POTENTIALLY SIGNIFICANT RELEASES
Technologies
Ion Exchange
Chemical Treatment
Biological Treatment
Air
• None likely
• Fugitive emissions of volatile
organic compounds from
treatment tanks
* Emissions of volatile organics
in aerobic treatment or due
to aeration
Water"
• Discharge of backwash water
• Discharge of effluent with
treatment residues
» Discharge of effluent with
unremoved solids
Other11
• Disposal and/or regeneration
of spent resins
• Disposal of treatment
sludges
• Disposal of treatment
sludges
Membrane Separation
Reverse Osmosis
Electrodialysis
• None likely
• None likely
• Discharge of effluent
containing unfiltered organics
(depends on filter membrane
used)
• Discharge of treated effluent
• Discharge of concentrate
stream with contaminants
removed from treated water
/•
• Discharge of concentrate
stream with contaminants
removed from treated water
Notes:
a In genera], seepage and leaching are more likely to affect ground water, but could also contaminate surface water. Runoff and discharge are releases that will most
likely contaminate surface water, but could also contaminate ground water.


b Other releases include treatment residuals that need further treatment or proper disposal. In most cases, this column refers to sludge or solid residues that may also
be hazardous.                                                                                               •

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                          REFERENCES FOR APPENDIX A
Peavy, Howard S., Donald R. Rowe, and George Tchobanoglous.  1985. Environmental Engineering. McGraw-
Hill, New York.

U.S. Environmental Protection Agency (EPA). 1987. A Compendium of Technologies Used in the Treatment
of Hazardous  Wastes.  Center for Environmental Research Information.  EPA/625/8-87/014 (NTIS PB90-
274093/XAB).

EPA. 1988. Technology Screening Guide for Treatment ofCERCLA Soils and Sludges. Office of Research and
Development. EPA/540/2-88/004 (OSWER Directive 9380.0-25, NTIS PB89-132674).

EPA. 1989. Summary of Treatment Technology Effectiveness for Contaminated Soil.  Office of Emergency and
Remedial Response. EPA 540/2-89/-53.

EPA. 1990. National Technical Guidance Series, Air/Superfimd Manual, Volume 3.  Office of Air Quality
Planning and Standards.  EPA-450/1-89-003 (NTIS PB89 180061/AS).

EPA. 1990.  The Superfund Innovative Technology Evaluation Program, Progress and Accomplishments Fiscal
Year 1989. Office of Solid Waste and Emergency Response. EPA/540/5-90/001 (NTIS PB90-216516/XAB).

EPA. 1991.  Comments from Laurel Staley, Ed Bates, Ron Lewis, Teri Shearer, John Herrmann,  Paul
dePercin, Ed Earth. Coordinated by Mary Gaughan, Superfund Technology Demonstration Group, Cincinnati,
Ohio.
                                             -42-

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                                 APPENDIX B

 QUANTIFYING POTENTIAL RELEASES  FROM
   SELECTED  REMEDIATION TECHNOLOGIES
    Remediation activities at hazardous waste sites
have the potential to cause emissions and impacts
in addition to those being addressed.  Potential
emission sources during remediation include point
sources of treatment residuals such as incinerator
stacks;   fugitive   emissions   from  treatment
equipment leakage; and areal sources of volatile
organics and fugitive  dusts from the  disturbed
surface of a contaminated land area.  Uncontrolled
releases can result in exposures to contaminants in
soils, surface water, ground water, and ambient air
surrounding  the  treatment  equipment. .  The
following sections provide descriptions of several
common  remediation  activities  to  serve  as
examples  of  the considerations  involved  in
quantifying  technology-specific  releases.   This
appendix also contains a list of references that can
be useful in quantifying potential air releases for a
variety of remediation technologies.

B.1   SOILS HANDLING
       TECHNOLOGIES

    Soils handling is a major component of nearly
all ex-situ technologies for treating contaminated
soils. Soil handling activities include: excavation;
transportation (e.g., to storage or treatment areas);
dumping (e.g., onto trucks or  piles); storage; and
grading the treated or replaced soil.  Any or all of
these  activities  may  result  in  fugitive  dust
emissions,  the main type of  release from soils
handling.  These  emissions  can  carry organic
and/or  inorganic  contaminants, which  may be
bound to soil particles, for great distances away
from the site.  Soil handling activities also can
increase volatile organic emissions by exposing
contaminated soil to the atmosphere, and through
agitation of the soil.

    Some of the important parameters that may
affect the fugitive dust emissions potential at a
contaminated site are listed  in the box below.
These parameters depend on site and remedial
activity characteristics.   Details can be obtained
from onsite observation or from.vendors and/or
operators.  Some or all of these parameters may
already  have  been considered  in  the  RI/FS.
Fugitive dust  emission factors (mass, per unit
operation) or rates (mass per unit time, derived
from  emission factors) for  volatile.  organic,
paniculate and/or metal contaminants during each
soil handling remedial activity can be estimated
using equations and procedures outlined in the
documents listed in Section B.4.  These emission
factors or rates can be used as inputs to fate and
transport models, which are used to generate
exposure  point  concentrations.    Additional
information on  exposure  assessment  can be
obtained from Chapter 2 of this guidance and
Chapter 6 of RAGS/HHEM Part A,
      KEY PARAMETERS AFFECTING
    RELEASES FROM SOILS HANDLING

     Area of working surface
     Agitation factor
     Drop height (when transferring soil)
     Storage pile geometry
     Soil moisture content
     Soil silt content
     Meteorological conditions
     Chemical characteristics
B.2    THERMAL DESTRUCTION
       TECHNOLOGIES

   Thermal destruction uses  high temperature
and controlled conditions to oxidize and/or degrade
a substance into simple combustion products such
as CO2, H2O vapor, SO2, NOX, HC1 gases, and ash.
Thermal destruction  methods  can be  used to
destroy organic contaminants in  liquid, gaseous,
and solid waste streams. Incinerators are by far
the best known and  most  studied  thermal
destruction devices.    In many  cases,  thermal
destruction techniques that do not have sufficient
                                           -43-

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emission data can be assumed to have emission
characteristics similar to incinerators.

    Emission sources from incinerators include
process   emissions    and  fugitive   emissions.
Incinerator process  emissions include stack gas,
bottom  ash,  and air  pollution control device
residuals. Fugitive emissions include uncontrolled
or  undetected   equipment  leakage.    Process
emission   estimation   methods   for  organic
compounds, metals, particulates, and  acid gases
(HC1, SO2, and HF) can be obtained  from EPA
(1985a)  (see  Section  B.4.1).   Fugitive emission
sources and equations for estimating emissions are
detailed in EPA (1989) (see Section  B.4.1) and
Holton  and Travis (1984) (see Section B.4.3).
Fugitive  emissions from soils handling prior to
incineration can be  estimated using the guidance
given in Section B.I on soils handling.

    Emissions   from   thermal   destruction
technologies generally can be estimated using any
one of the approaches listed below.   (These
methods do not directly account for removal of
contaminants by air pollution control devices that
may be  used to treat  emissions  from thermal
destruction devices.)

•   Default approach: Thermal destruction devices
    at most contaminated sites may be required to
    meet   the  requirements   under   federal
    regulations  such as  RCRA  or  the Toxic
    Substances  Control Act (TSCA), since these
    requirements are generally considered ARARs.
    RCRA requires at  least  99.99% destruction
    and removal of regulated  organic constituents
    from  wastes.    TSCA  requires 99.9999%
    destruction and removal for wastes containing
    PCBs and  dioxins.  Thus, organic emissions
    from thermal destruction of hazardous waste
    can be estimated by assuming  that the above
    requirements of  RCRA and TSCA will be
    exactly met, for pollutants covered  by those
    regulations. Similar requirements can be used
    to estimate HC1 emissions, but this approach
    may not provide estimates for paniculate or
    air  emissions.

 •  Trial run approach: Federal regulations such
    as RCRA  and  TSCA require trial  burns to
    demonstrate removal efficiencies. Whenever
    trial burn data  for the waste in question exist
    they can be used to estimate the emissions
    that  might  occur  during  actual  remedy
    implementation.   Data  obtained from  trial
   burns at different sites or different operable
   units. from the same site can  be used for
   estimating emissions.

•  Theoretical   or   empirical   approach:
   Theoretical or applicable empirical equations
   — often called models — can be  used to
   estimate emissions.  These models correlate
   incinerator operating parameters and pollutant
   emission rates.

   Some of the important parameters that  may
affect the  emissions  associated  with  thermal
destruction technologies  are  listed  in  the  box
below.   Many of these  parameters  are  device
dependent  and  can  be  obtained  from  onsite
observation or from vendors and/or operators.
       KEY PARAMETERS AFFECTING
        RELEASES FROM THERMAL
               DESTRUCTION

       Waste feed rate
       Burn temperature
       Residence time
       Excess air rate
       Facility size/type
       Atomization
       Control device efficiency
       Chemical characteristics
B.3    SOLIDIFICATION/
        STABILIZATION
        TREATMENT
        TECHNOLOGIES

    Solidification/stabilization  technologies  are
used  to  immobilize  the toxic  and  hazardous
constituents  in  the waste  by changing  those
constituents into immobile forms, binding them in
an immobile, insoluble matrix, and/or binding them
in a matrix that minimizes  the material surface
• exposed  to  solvents.    Except  for  emerging
technologies that  involve in-situ  treatment, the
implementation  of stabilization or solidification
generally involves  several of the soils handling
activities discussed in Section B.I.  The box below
lists some of the key parameters affecting releases
associated with solidification/ stabilization.  These
parameters  depend   on   the   specific
                                                -44-

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solidification/stabilization process.  These can be
obtained from onsite observation or from vendors
and/or operators.
       KEY PARAMETERS AFFECTING
              RELEASES FROM
      SOLIDIFICATION/STABILIZATION
        TREATMENT TECHNOLOGIES

       Binder type
       Batch size
       Waste/binding agent ratio
       Mixing time/efficiency
       Curing time
       Meteorological conditions
       Chemical characteristics
B.4   REFERENCES FOR
       DETERMINING RELEASES
       RESULTING FROM
       REMEDIAL ACTIVITIES

    Provided  below  are references  containing
discussions  of   remedial   activities   and
methodologies for determining releases associated
with these  activities.   The  references presented
under the heading of various remedial activities
contain  information  regarding the majority of
remedial  activities that  may  occur  at a  site
(including soils handling, thermal destruction, and
stabilization/solidification).     The   remaining
references  contain information specific  to  the
activity listed  in the heading.  See the references
provided for the main text of RAGS/HHEM Part
C, especially the RI/FS Guidance (EPA 1988c), for
additional references.

B.4.1   VARIOUS REMEDIAL ACTIVITIES

Primary References

Environmental Protection Agency (EPA). 1985a.
    Handbook: Remedial Action at Waste Disposal.
    Sites (Revised). Hazardous Waste Engineering
    Research   Laboratory.    EPA/625/6-85/006
    (NTIS PB87-201034/XAB).

    Provides  information   on   remedial
    technologies,   selection   of  appropriate
    remediation technologies  for a given waste
    site, and planning remedial activities.  Includes
    discussions of onsite and offsite disposal  of
    wastes and soil, removal and containment  of
    contaminated   sediments,  and  in-situ
    treatments.

EPA.  1989.  Estimation of Air Emissions from
    Cleanup   Activities   at   Superfund   Sites.
    Air/Superfund National Technical  Guidance
    Study Series, Volume 3. Office of Air Quality
    Planning and Standards.   EPA/450/1-89/003
    (NTIS PB89-180061/XAB),

    This  , document  provides   a   step-by-step
    protocol  for  estimating  air  quality  impacts
    resulting from  site  remediation.   Presents
    emissions  estimation techniques for  thermal
    destruction devices,  air stripping of ground
    water,  in-situ venting, soils handling,  and
    solidification/stabilization.

Additional References

EPA.  1990.   Emission Factors for  Superfimd
    Remediation Technologies.  Draft.  Office  of
    Air Quality Planning and Standards.

EPA.   1988.    Superfund  Removal Procedures
    Revision Number Three.  Office of Emergency
    and Remedial Response.  OSWER Directive
    9360.03B.

EPA  1986.   Superfund  Remedial Design  and
    Remedial  Action  Guidance.   Office   of
    Emergency and Remedial Response. OSWER
    Directive 9355.0-4A.

B.4.2   SOILS HANDLING

Primary References

EPA. 1985b. AP-42: Compilation of Air Pollution
    Emission Factors, Fourth Edition.  Office  of
    Air and Radiation. NTIS PB86-124906.

    This  document  contains  emissions  data
    obtained from source tests,  material  balance
    studies,  engineering estimates, and other
    sources.  Emission factors and equations are
    derived  from sand  and  gravel  processing
    (Section 8.19.1), crushed  stone operations
    (Section 8.19.2), surface coal mining (Section
    8.2.4), and fugitive dust sources (Section 11.2).
                                              -45-

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EPA.  1985c.  Rapid Assessment of Exposure to
    Particulate   Emissions   from   Surface
    Contamination Sites.  EPA/600/A-85/002.

    This document  provides a  methodology for
    rapid assessment  of  inhalation  exposures to
    respirable particulate emissions  from surface
    contaminated sites. The methodology consists
    of a site  survey  procedure and  particulate
    emission  factor  equations  for  wind  and
    mechanical entrainment processes.

EPA.  1990.  Development of Example Procedures
    for Evaluating   the  Air  Impacts  of  Soil
    Excavation Associated with Superfund Remedial
    Actions.  Office of Air Quality Planning and
    Standards.   EPA/450/4-90/014 (NTIS  PB90-
    255662/XAB).

    This   document   identifies   and   defines
    computational requirements for estimating air
    impacts from remediation of CERCLA sites.
    The estimation  of  air impacts  from two
    example sites employing soil excavation are
    discussed.    Modified  Research  Triangle
    Institute (RTI) land  treatment equations are
    used   for  calculating   emissions   from
    excavations.

Additional  References

Baxter, R.A. and D.M. Wilbur.  1983. Fugitive
    Particulate Matter and Hydrocarbon Emission
    Factors from Mining, Handling,  and Storing
    Diatomite.   AeroVironment, Inc.   Pasadena,
    California.

EPA.   1977.  Technical  Guidance for Control of
    Industrial   Process    Fugitive    Particulate
    Emissions. Office of Air Quality and Planning
    Standards.  EPA/450/3-77/010 (NTIS PB-272
    288/2).

EPA.   1985d.   Modeling Remedial  Actions  at
     Uncontrolled Hazardous Waste Sites. Office of
     Emergency and Remedial Response, Office of
     Solid  Waste  and  Emergency   Response.
     EPA/540/2-85/001   (OSWER   Directive
     9355.0-8).

Orlemann, J.A.  and G.A. Jutze. 1983.  Fugitive
     Particulate Dust Control Technology.   Noyes
     Publications. Park Ridge, New Jersey.
B.4.3   THERMAL DESTRUCTION

Primary References

Holton, G.A. and C.C. Travis.  1984.  Methodology
    for   Predicting   Fugitive   Emissions   for
    Incinerator Facilities. Environmental Progress
    3:2.  Oak Ridge National Lab., Health  &
    Safety Research Division. Oak Ridge, TN.

    Error analysis  and Monte Carlo  modeling
    techniques  are  used  to  predict  fugitive
    emissions  caused  by  leaky  pump  fittings,
    sampling connections, flanges, storage tanks,
    and  other  non-stack  equipment.     Ten
    equations and three parameter value tables are
    provided for emission calculations.

Travis,  C.C.,  E.L. Etnier, G.A.  Holton,  F.R.
    O'Donnel,  and   D.M.  Hetrick.     1984.
    Inhalation  Pathway  Risk  Assessment  of
    Hazardous Waste Incineration  Facilities.  Oak
    Ridge National Lab. Oak Ridge, Tennessee.
    ORNL/TM-9096.

    This report evaluates the relative importance
    of plant design and waste physicochemical
    variables on human inhalation  exposure and
    health risk using two hypothetical incineration
    facility designs of three  sizes each,  burning
    three different  generic  wastes.   Fugitive
    emissions are calculated  using  equations
    relating  incinerator  facility  operation and
    configuration to fugitive emissions.

Trenholm, A. and D. Oberacker. 1985.  "Summary
    of Testing  Program  at  Hazardous  Waste
    Incinerators."   Proceedings —  Annual  Solid
    Waste Research Symposium.  Environmental
    Protection Agency. Cincinnati, Ohio. Report
    No. CONF-8504112.

    This article summarizes  the  results  of tests
    conducted  at eight  full-scale  hazardous
    incineration facilities.

Additional References

Cheremisinoff, P.N.    1986.   "Special  Report:
    Hazardous Materials and Sludge Incineration."
    Journal  of  the  Air  Pollution  Engineering
    18:12(32-38).
                                                -46-

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 EPA. 1984. Performance Evaluation of Full-scale
    Hazardous   Waste   Incinerators.      (Five
    volumes.) Industrial Environmental Research
    Laboratory.  Cincinnati, OH.  EPA-600/2-84-
    181 a-e (NTIS PB85-129500).

'Lee,  C.C., G.L.  Huffman, and  D.A.  Oberacker.
    1986.  "Hazardous/Toxic Waste Incineration."
    Journal of the Air Pollution Control Association
    36:8.

 Oppelt, E.T.  1987.  "Incineration of Hazardous
    Waste, A Critical Review." Journal of the Air
    Pollution Control Association. 37:5.

 Staley, L.J., G.A. Holton, F.R. O'Dormel, and C.A.
    Little.   1983.  "An Assessment of Emissions
    from a Hazardous Waste Incineration Facility,
    Incineration  and  Treatment of  Hazardous
    Waste."  Proceedings of the Eighth Annual
    Research Symposium.  EPA-600/9-83/003.

 Wallace, D.D.,  A.R. Trenholm,  and D.D. Lane.
    1985.  "Assessment of Metal Emissions from
    Hazardous Waste Incinerators." Proceedings —
    78th APCA Annual Meeting. Paper 85-77. Air
    Pollution Control Association.  Pittsburgh,
    Pennsylvania.
 B.4.4   STABILIZATION/SOLIDIFICATION

 Primary References

 Cullinane, M.J., L.W. Jones, and P.O. Malone.
    1986. Handbook for Stabilization/Solidification
    of  Hazardous  Waste.    Hazardous  Waste
    Engineering Research Laboratory. EPA/540/2-
    86/001.

 Hill,  R.D.  1986.  Stabilization/Solidification of
    Hazardous  Waste.     Hazardous   Waste
    Engineering  Research  Lab.    EPA/600/D-
    86/028.

    This document discusses techniques such as
    sorption,  lime-fly ash  Pozzolan  process,
    Pozzolan-Portland   process,   thermoplastic
    microencapsulation, and other techniques.

Additional References

Cullinane, MJ. and L.W. Jones.  1985.  Handbook
   for  Stabilization/Solidification  of  Hazardous
    Waste.     Prepared    for:   Environmental
    Protection   Agency,    Hazardous   Waste
    Engineering Research Laboratory.  Office of
    Research and Development.   EPA/540/2-86-
    001.
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                                   APPENDIX  C
              SHORT-TERM  TOXICITY VALUES
     The  short-term ^ effectiveness  criterion 'for
 evaluating  remedial' alternatives  includes  an
 evaluation of the risks due to the short-term
 exposure of populations to contaminants during
 remedy  implementation.   Such short-term risks
 generally include both baseline risks from existing
 site contamination and new risks that would occur
 during the implementation of a remedy.  In some
 cases, potential exposures and risks due to short-
 term exposures should be quantitatively assessed;
 however, there is no simple or widely accepted
 method for estimating such risks. Therefore, in all
 cases where short-term toxicitv values are needed.
 TSC should be consulted.  EPA's Environmental
 Criteria  and  Assessment Office (ECAO; where
 TSC is located) will maintain the data files for the
 most appropriate short-term  toxicity values for
 evaluating risks from remedial alternatives.  To
 obtain the most up-to-date information, regional
 EPA CERCLA staff must contact:

    Superfund Health Risk Technical
     Support Center
    Environmental Criteria and Assessment Office
    U.S. Environmental Protection Agency
    Mail Stop  114
    26 West Martin Luther King Drive
    Cincinnati, OH  45268
    Phone: 513-569-7300 (FTS-684-7300)
    FAX: 513-569-7159 (FTS-684-7159)

    Requests from others must be submitted to the
TSC in writing and must contain  the following
information for consideration:

 •   CERCLA site name, site location, and 12-digit
    site number;

•   name and phone number of the RPM; and

•   detailed  description of the  risk assessment
    related question.

    The remainder of this appendix provides some
general background on exposure duration issues
and an .overview of some of the existing methods
 for  deriving short-term  human health  toxicity
 values.

 C.1   BACKGROUND ON
        EXPOSURE DURATION

     In  assessing  short-term  risks of remedial
 alternatives, the time  frame (e.g., hours,  days,
 weeks up to seven years) is generally of a much
 shorter  duration  than  that identified  in  the
 baseline risk assessment.  Nevertheless, there are
 a number of types of toxicity values that have been
 developed to characterize risk due to these short-
 term exposures.  Some of these  types depend on
 concentration- or dose-based threshold limits that
 are  used as guidance  levels for protection of
 specific populations from specific exposures (e.g.,
 guidance levels intended to protect healthy workers
 from daily occupational exposure to chemicals in
 the  workplace).   In this section, the types of
 exposure durations commonly suggested or implied
 by the toxicity value types (discussed later)  are
 presented.

    Releases  that  may  occur  during  remedy
 implementation could last for varying durations
 but are expected, in most if not all cases, to give
 rise to less-than-lifetime exposures. Furthermore,
 releases that occur during remediation may result
 in  exposure  levels  much  higher than those
 preceding remediation.  Different risk levels may-
 be  associated with  these   different exposure
 durations (assuming the same dose rate) and with
various exposure concentrations.  Therefore, it is
important that the  dose-  or concentration-based
 toxicity values that are chosen to  characterize the
short-term risks be based on appropriate exposure
durations.  Exposure durations  associated with
existing methods for characterizing short-term risks
include  hours, days,  weeks,  months,  and years
(generally up to seven years).

    Currently, RAGS/HHEM Part A defines three
exposure durations, apart from long-term exposure,
that may be of concern at CERCLA sites:  single
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exposure event, very short-term exposure,  and
short-term (subchronic) exposure.

•   Single  Exposure Event.   The  majority of
    chemicals are capable of producing an adverse
    health effect after  a single exposure event,
    depending on the intensity of exposure.  For
    developmental   toxicants,  irritants,   and
    neurological  poisons,  a  single, low  level
    exposure event  can result in  effects  after
    minutes, hours, or a day.

•   Very Short-term Exposure.  For some acute
    toxicants, multiple exposures over several days
    could result in an adverse effect. For  these
    chemicals, the exposure is assessed over days
    or weeks (up to two weeks).

•   Short-term (Subchronic) Exposure. Exposure
    lasting anywhere from  two weeks  to seven
    years to low concentrations of a chemical can
    also  produce adverse effects; this exposure is
    assessed  by averaging  it  over  the specific
    duration.

    During evaluations of remedial alternatives, it
may be important to assess exposure (and risk or
hazard) for all relevant  exposure durations.  Both
the shortest time period of exposure, from peak or
accidental releases,  to  the  cumulative  exposure
over  the entire  time period of  the remedy
implementation,  may   need  to be considered.
Quantitative assessment is  contingent,  however,
upon  the  availability  of  adequate   exposure
characterization.  Exposure models used to predict
concentrations  have not for the most  part been
validated over the short durations considered for
single exposure events (e.g., minutes to hours). At
best, meteorological data  are collected on an
hourly basis at a site removed from the location of
interest;  using these data  to derive a  model to
predict  exposure concentrations  for   durations
shorter than those for the meteorological data may
produce results  that   could  not  be  supported
scientifically.  In addition,  the need to evaluate
peak .exposures as well as  longer-term average
exposures during remedy implementation depends
on a  number of considerations,  including  the
degree of risk or hazard associated with the longer-
term exposure  and the difference  between  the
predicted   peak  and   average  exposure
concentrations.

     A review of the types of (duration-specific)
 toxicity values that are available (discussed later in
this appendix) indicates that a number of the types
correspond to various  durations that are relevant
to  releases  during  remedy  implementation.
Because a toxicity value  generally is specific to a
certain duration, however, risk may need to  be
characterized separately  for the three short-term
exposure durations.

C.2   EXISTING SHORT-TERM
       TOXICITY VALUES

    In this section, commonly encountered short-
term toxicity values are summarized.  These values
are: (1) concentration and dose threshold values
primarily  for  noncarcinogenic  effects;  and  (2)
specific short-term carcinogenic risk values.  A
section is provided on each of these toxicity value
categories.

C.2.1   TOXICITY VALUES FOR ASSESSING
       RISK OF NONCARCINOGENIC
       EFFECTS FOR  SHORT-TERM
       EXPOSURE

    Toxicity values designed to characterize the
risk of noncarcinogenic effects are summarized in
the following subsections. Further information on
the suitability of these values for various CERCLA
exposure scenarios can be obtained from the TSC.

C.2.1.1  Developmental Toxicant Reference Dose
        (RfDdt) and Reference Concentration
        (RfCdl)

    RfDdts and RfCdts are developed for chemicals
that have been shown  to cause adverse effects in a
developing  organism.   EPA's Human Health
Assessment Group of the Office of Health and
Environmental Assessment is  in  the  process  of
developing  RfDdt  and RfCdt values  and  the
methodology for their derivation. As proposed by
EPA (EPA 1989b), these values.will likely be
derived from the no-observed-adverse-effect-level
(NOAEL) or lowest-observed-'adverse-effect-level
(LOAEL)  in  a  manner consistent  with  the
derivation of reference doses (RfDs) and reference
concentrations (RfCs), and without adjustment for
short exposure duration. RfDdts are expressed in
terms of dose and RfCdts are expressed as an air
concentration.   Additional information on  these
criteria   is   available    in   EPA's   Proposed
Amendments  to the  Guidelines for  the Health
Assessment of Suspected Developmental Toxicants
 (EPA 1989b), or by contacting the Reproductive
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and  Developmental Toxicology  Branch  of the
Office of Health and Environmental Assessment at
202-260-7331 (FTS-260-7331).

    Currently (i.e., at the date of publication of
this guidance), developmental toxicity is considered
in   the  derivation   of   EPA   criteria   for
noncarcinogenic effects (including RfDs and  RfCs
for subchronic and chronic exposure and drinking
water Health Advisories [HAs]).  That is,  these
criteria  are set at levels considered protective for
developmental  effects  as  well  as   for  other
noncarcinogenic effects.

C.2.1.2  Subchronic Reference Dose (RfDs) and
        Reference Concentration (RfCs)

    RfDss and RfCss are developed by ECAO and
are used to characterize potential noncarcinogenic
effects associated with short-term exposures  (two
weeks to seven years as defined in  RAGS/HHEM
Part A). To date, approximately 305 RfDss and 60
RfCss have been published. These RifDs and  RfCs
are developed based on NOAELs or  LOAELs
identified from subchronic (i.e., usually j>90 days
but less-than-chronic) toxicity studies.  RfDss are
expressed in terms of dose and RfCss are expressed
as air concentrations. Subchronic RfDs and  RfCs
are available in HEAST. The derivation of RfDss
is described in  more  detail in  RAGS/HHEM
Part A.

C.2.1.3  One-day, Ten-day, and Longer-term
        Drinking Water Health Advisories (HAs)

    Drinking  water HAs   developed  by  EPA
provide  guidance to assist state and local officials
responsible  for public  health protection  during
emergency  situations  involving drinking water
contamination.  HAs are derived in  a manner
reasonably consistent with oral RfD methodology.
Accordingly, these HA values constitute suitable
criteria  for  evaluating short-term  oral exposure.
The HA concentrations include a margin of safety
to protect  sensitive members of the  population
(e.g.,  children, the  elderly, pregnant  women).
"One-day HA" is the term used to describe the
concentration of a chemical in drinking water that
is  not   expected  to   cause   any   adverse
noncarcinogenic effects for one day of exposure,
with a  margin of safety.    The  "Ten-day  HA"
describes  the concentration of  a chemical  in
drinking water that is not expected to cause any
adverse  noncarcinogenic health effects  for two to
ten consecutive days of exposure, with a margin of
safety. The "Longer-term HA" is the concentration
of  a chemical  in drinking  water  that  is  not
expected  to  cause any adverse noncarcinogenic
effects  up  to  approximately  seven  years  of
exposure.  ("Lifetime HAs" that are protective for
exposure over a lifetime are also developed based
on  chronic RfDs.)

    In  general,  the  HAs  described  here  are
protective of only noncarcinogenic effects.  These
values are expressed as concentrations in drinking
water but can be converted to mg/kg/day doses by
using the assumptions that were applied in their
calculation: consumption of 1 L/day by a 10 kg
child (one-,  ten-, and longer-term HAs) and  2
L/day   by   a  70-kg   adult   (lifetime   HA).
Approximately 140 HAs  have been developed by
EPA for each exposure duration. (HAs are briefly
described in RAGS/HHEM Part A.)

C.2.1.4  Acute Inhalation Criteria (AIC)

    A report describing the derivation of AICs for
benzene and beryllium is available through  the
TSC. AICs are derived as criteria for single, short-
duration (up to an hour or a few hours) inhalation
exposures, as may occur  from releases  during
remediation.  The AICs  are based on noncancer
endpoints and are expressed as air concentrations.
AICs have been derived  for a  limited number of
chemicals using EPA RfC methodology, modified
as required for this acute exposure scenario. The
modification consists  of  using the NOAEL  (or
LOAEL)   as  reported  in  the  study without
adjustment for exposure duration (hours/24 hours).
Because these criteria are conceptually consistent
with inhalation RfCs,  they are a good basis  for
assessing short-term risks from single, very short
exposures.  The TSC should be contacted  for
additional AIC values.

C.2.1.5  Minimal Risk Levels (MRLs)

    MRLs are derived by the Agency  for Toxic
Substances and Disease-Registry (ATSDR) from
human or animal studies  for threshold effects on
chemicals  found  at CERCLA hazardous  waste
sites. MRLs are developed for both inhalation  and
oral exposures; oral MRLs are expressed as doses
and  inhalation   MRLs  are   expressed   as
concentrations in air.   Estimates of exposure
posing minimal risk to humans are made for  the
most sensitive noncarcinogenic endpoint (including
developmental and reproductive endpoints)  for
three different exposure durations  (i.e.,  acute,
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intermediate, and chronic).    These  exposure
durations  for which  MRLs are derived are as
follows: acute MRL — 1 to 14 days; intermediate
MRL — 15  to 364 days; chronic MRL — .>365
days.  MRLs are developed using an approach that
is  consistent with EPA RfD  methodology (i.e.,
identification of a  NOAEL or  LOAEL  and
application of uncertainty factors to reflect human
variability and, where appropriate, the uncertainty
of extrapolating from laboratory animal data to
humans).

    Acute inhalation  MRLs  differ from AIC in
regard to adjustment for exposure duration.  The
guidance for derivation of acute inhalation MRLs
specifies that "exposure periods of less than 24
hours in the toxicity study from which the MRL is
derived, can be adjusted  to  one day"  (ATSDR
1991); this adjustment is commonly carried out.
No such adjustment is carried out in the derivation
of AICs, which are intended to serve as guidance
for acute, very short, and single, exposures (e.g.,
ranging from less than an hour to a few hours,
perhaps  as    inadvertent   releases   during
remediation).

    MRLs  can   be   found  in  the  ATSDR
Toxicological Profile documents in the  Health
Effects  Summary section,  on the   Levels  of
Significant Exposure figure (graph).  The bottom
of the dotted line on the graph  represents the
MRL. Except in the earliest ATSDR Toxicological
Profiles, MRL values and the endpoints on which
they  are based are  also identified in the text
accompanying the figure.  To date, approximately
62 acute MRLs (38 oral, 24 inhalation) have been
derived by  ATSDR.   As with other  short-term
 toxicity values, guidance regarding use of the MRL
 must be sought from  the TSC.

 C.2.1.6 Emergency Exposure Guidance Level
         (EEGL), Short-term Public Emergency
         Guidance Level (SPEGL), and
         Continuous Exposure Guidance Level
         (CEGL)

     EEGLs and  CEGLs are exposure guidance
 levels developed by the National Research Council
 (NRC 1986) specifically for military  personnel
 operating under emergency conditions. Therefore,
 setting of  these levels involves consideration  of
 various factors (such as age distribution, length of
 exposure, and susceptibility) that are different from
 those  related to  the general population.  These
 guidance levels are published in the NRC (1984-
1988)  Emergency   and  Continuous  Exposure
Guidance   Levels  for   Selected   Airborne
Contaminants. To date, 43 chemicals have been
evaluated by NRC.

    The EEGL is defined as the air concentration
of  a  substance  that  is  acceptable  for   the
performance   of   specific  tasks  during  rare
emergencies usually lasting from  1 to 24 hours
(i.e., it is a  ceiling guidance  level for a single
emergency  exposure) (NRC 1986).  EEGLs are
intended to prevent irreversible harm or  serious
impairment  of   judgment   or   performance.
Exposure at an EEGL might produce reversible
effects, and therefore should not be considered
hygienic or safe.   Acute toxicity  is the primary
basis for establishing an  EEGL.   However,  even
brief exposure to some substances might have the
potential to increase the risk of cancer or other
delayed effects. '  Derivation  of  an EEGL may
involve application of an uncertainty factor of ten
to extrapolate from animal data to humans, but no
other  species adjustments are applied.   Some
EEGLs are based on extrapolation of oral  data.
EEGLs are based on the most sensitive or  most
important  noncarcinogenic health effects  known.
Because EEGLs are derived  for healthy military
personnel  during rare emergencies, and are not
intended to protect against reversible effects, they
should not be  applied  directly  to the  general
population (NRC 1986).

     The  SPEGL  is   defined   as  a  suitable
concentration for  unpredicted, single, short-term
emergency exposure of 1 to 24 hours of the general
 public. SPEGLs take into account the wide range
 of susceptibility of the general public. The SPEGL
 is generally estimated by applying an uncertainty
 factor of two to ten to the EEGL, to account for
 sensitive groups — such as children, the elderly,
 and persons with serious debilitating  diseases.
 NRC  (1986) suggests that a  safety factor of two
 (i.e., EEGL x 0.5) is appropriate to protect more
 sensitive groups, such as children or the elderly,
 and that a safety factor of ten (i.e., EEGL x 0.1) is
 appropriate for fetuses or newborns.  Because the
 SPEGL   is  derived   from  the  EEGL,   the
 considerations discussed above with regard to the
 EEGL also apply to SPEGLs.

     The   CEGL  is   defined  as  a   ceiling
 concentration of a chemical in air to which military
 personnel can  be exposed  for  up to  90  days
 without immediate or delayed adverse effects or
 degradation of performance (NRC 1986). CEGLs
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 are not derived for carcinogens.  When data from
 chronic studies are available, they can be used to
 derive CEGLs.  A CEGL is generally estimated,
 however, by applying an uncertainty factor of 10 to
 100  to the EEGL (i.e., EEGL x 0.01  to 0.1),
 depending on the evidence  for detoxification or
 accumulation of the substance in the body. Where
 there is evidence  of substantial  detoxification, a
 safety  factor of  ten  is recommended by NRC
 (1986). If there is no evidence of detoxification or
 detoxification is slow, a safety factor of 100 might
 be more appropriate. If the substance accumulates
 in tissues,  such  as  halogenated biphenyls  and
 metals, even higher factors are recommended by
 NRC (1986). Other considerations discussed with
 regard to the EEGL also apply to CEGLs derived
 from EEGLs.

 C.2.1.7  Threshold Limit Values — Short-term
        Exposure Limits (TLV-STELs),
        Threshold Limit Values — Time-
       weighted Averages (TLV-TWA), and
        Threshold Limit Values — Ceiling
        (TLV-C)

    TLVs are concentrations developed  by the
 American Conference of Governmental Industrial
 Hygienists  (ACGIH) to protect workers from
 adverse effects  of  occupational  exposure  to
 airborne   chemicals.      However,  because
 occupational exposure limits are  not intended to
 protect sensitive workers or other populations, are
 not intended for the assessment of community air
 pollution  or  continuous  exposure,  may  not
 incorporate the most recent lexicological data, may
 be based on unpublished documentation that is not
 available for review, and  may differ from EPA
 derivations  with  respect  to weight-of-evidence
 considerations and use of uncertainty factors, EPA
 does not endorse  the general use of occupational
 exposure  limits  in deriving  EPA criteria.   In
 addition, it should be noted  that the TLVs for a
 fair number of chemicals are derived by analogy to
 other chemicals because health effects data are
 inadequate or lacking.

   The TLV-STELs are 15-minute time-weighted
average (TWA)  exposures that  should  not  be
exceeded at  any time during  the eight-hour work
day/40-hour workweek and should not occur more
 than four  times a day, with at least  60 minutes
between successive exposures in the STEL range
 (ACGIH 1990). The TLV-STEL  is established to
 prevent workers from suffering irritation, chronic
or irreversible  tissue  damage,  or  narcosis  of
 sufficient degree to increase  the  likelihood of
 accidental injury. Use of the TLV-STEL should be
 limited to very short,  single exposure  events.
 STELs are recommended for substances with acute
 effects recognized from high short-term exposures
 in  either humans  or animals (ACGIH  1990).
 Approximately   115  TLV-STELs  have  been
 published by ACGIH.

    The TLV-TWA is the time-weighted average
 concentration for a normal eight-hour workday/40-
 hour workweek to which nearly all workers may be
 exposed, day after  day,  without  adverse  effects.
 The TLV-C is a concentration that should not be
 exceeded during any part of the working exposure.
 The ACGIH uses the TLV-C for substances that
 are particularly  fast acting and  hence are best
 controlled by a  ceiling limit.  In excess  of  500
 TLV-TWAs and fewer than 50 TLV-Cs have been
 published by ACGIH.                .

 C.2.1.8 Permissible Exposure Levels (PELs) and
       Recommended Exposure Limits (RELs)

    PELs are enforceable occupational exposure
standards  developed by the Occupational Safety
and Health Administration (OSHA).  They  are
meant to protect workers against  catastrophic
effects (such as cancer; cardiovascular, liver, and
kidney damage; and lung diseases) as well as more
subtle effects  resulting in central nervous  system
damage, narcosis, respiratory effects, and sensory
irritation.  The PELs are generally adopted from
(existing) secondary guidance levels (e.g., ACGIH's
TLV-TWAs   and   TLV-STELs   and    the
recommended exposure limits [RELs] developed by
the National Institute for Occupational Safety and
Health [NIOSH]), and nearly  400  are available
from OSHA.  EPA's reservations concerning  the
use of TLVs as the basis for criteria to protect  the
general population (see Section C.2.1.7) apply also
to PELs and RELs.

C.2.1.9 Other Miscellaneous Methods

    The following are some  other methods that
risk assessors or RPMs may encounter.

•   Immediately  Dangerous to Life and Health
    (IDLH) Guidelines.    IDLH guidelines  are
    developed by NIOSH. These air concentration
    limits are for 30-minute exposures under what
    are essentially  emergency conditions,  and
    generally far exceed corresponding TLV-TWA,
    TLV-STELs or PELs.  IDLH guidelines were
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    determined only for the purpose of respirator
    selection. These guidelines are intended to be
    the maximum air concentration from which, in
    the event of respirator failure, a worker could
    escape within 30 minutes without experiencing
    any escape-impairing or irreversible health
    effects (NIOSH 1985).  Many  of the IDLH
    exposure levels are so high that they define
    levels   at   which  severe   toxic   effects
    (unconsciousness,  incapacitation,  intolerable
    irritation or death) would be likely (Alexeef et
    al. 1989). Therefore, the IDLH guidelines are
    not suitable as benchmark guidelines for acute
    exposure and may be higher than would be
    useful  even  as a guideline for  immediate
    evacuation.

•   CERCLA  Section   102 (a)  Reportable
    Quantities (RQs). RQs are developed by EPA
    based on, among other factors, acute toxicity,
    chronic  noncarcinogenic   toxicity,   and
    carcinogenicity.  RQs define the quantity in
    pounds  above which a release is considered
    potentially  hazardous (or, at least, warrants
    reporting)  under   CERCLA section 102(a).
    The  documentation for RQs  may  contain
    health effects  information that would be useful
    in determining criteria for short-term exposure
    but  are   not  by  themselves  useful   in
    characterizing risks from releases that might
    occur at a CERCLA site.

C.2.2  SPECIFIC  CARCINOGENIC RISK
       VALUES  FOR SHORT-TERM
       EXPOSURES
                 r
    There is relatively little guidance available on
characterizing risks from short-term exposure to
carcinogens. For cancer endpoints, most of the
currently available values are specific to lifetime
exposure.   Many experimental  investigations of
carcinogenicity  involve high-dose,  long-duration
exposure to compensate for the small number of
animals that are  used.  Carcinogenicity  data on
short-term  or  single  exposures  are  virtually
nonexistent  for  most  chemicals.   For  most
chemicals, the  current scientific view is  that  any
exposure, no matter how short in duration,  can
result in a carcinogenic risk. Characterizing  this
risk is complicated, however, because of factors
such as age at first exposure and mechanism of the
carcinogen's  action.      Consistent  with
RAGS/HHEM  Part A  and the Guidelines for
Carcinogen Risk Assessment (EPA 1986a),  the
preferred  approach   would  be  to   consider
cumulative dose, averaged over a lifetime.  This
method is discussed in Section C.2.2.1.

    Several investigators have reported additional
methods to characterize the effects from short-term
exposure to carcinogens.  Some of these methods
are currently being investigated by EPA but are
not  recommended  for  short-term  carcinogenic
assessments  at  this time.    However,  brief
summaries of these methods are provided below
with documentation for the interested  reader  to
pursue.

C.2.2.1  RAGS/HHEM Part A Method

    RAGS/HHEM Part  A currently recommends
that lifetime average exposures always be used  to
estimate carcinogenic risks. 'That is, because the
cancer toxicity values  (i.e., SFs) are  based  on
lifetime average exposures, Part A recommends
that less-than-lifetime exposures be converted  to
equivalent lifetime  values for the assessment  of
risk.  (This is also the. recommended approach  in
EPA's  Guidelines  for   Carcinogenic  Risk
Assessment [EPA  1986].)  In this manner, risks
from short-term exposures would be averaged over
a 70-year  lifetime, with modifications for specific
chemicals   if appropriate,  and,  therefore, may
appear to be relatively  minor in comparison  to
risks from longer-term exposures. While adjusting
less-than-lifetime  exposure  to  an  equivalent
lifetime exposure may be valid for relatively long
exposure durations, this adjustment for short-term
exposures  may  underestimate  the  risk for
"early-stage"  carcinogens  (i.e.,  DNA-damaging
agents).

C.2.2.2  Office of Research and Development
        (ORD) Interim Method for
        Vinyl Chloride

    EPA's ORD (EPA  1989a) used a study  by
Drew et al. (1983) to determine that the lifetime
carcinogenic  risk from vinyl chloride inhalation
increases when exposure occurs early in life.  Drew
et al. showed that  the effects from  exposure  to
vinyl chloride  depend  on  both age  at initial
exposure  and duration  of exposure.  His data
showed that children face higher risks than adults
for exposures of a given duration.  Cogliano stated
that  if risk for  partial lifetime  exposures  is
estimated by ignoring the age at  initial exposure
and considering only the duration, the risk will  be
underestimated for children and overestimated for
adults over 30. He proposed that risk for partial
                                                -54-

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 lifetime  exposure to  vinyl  chloride be:   (1)
 estimated as being proportional to the remaining
 lifetime of the exposed individual, and (2) adjusted
 depending on the length of exposure. The author
 also  stated  that,  at  this  time,  this analytical
 technique is applicable only to vinyl chloride arid
 should not be applied to any other substances.
 The TSC should be contacted for further guidance
 on assessing risks from vinvl chloride.

 C.2.2.3 EEGLs for Carcinogens

    The NRC (1986) has developed a method for
 deriving EEGLs (1 to 24-hour exposure guidelines)
 for inhaled carcinogens when the computed cancer
 risk associated with the toxicity-based EEGL (see
 Section C.2.1.6) is more than one in 10,000.  In
 these cases, the EEGL is lowered so that the  risk
 is not more than one in 10,000  (LslO"4). The NRC
 method draws on  the analysis of Crump and Howe
 (1984). and appears  to  employ a higher  level of
 acceptable lifetime  risk (i.e.,  IxlO'4) than  the
 RAGS/HHEM Part A method.  This method is
 discussed  in further detail in Criteria and Methods
for Preparing Emergency Guidance Level (EEGL),
 Short-term Public  Emergency Guidance Level
 (SPEGL), and Continuous Exposure Guidance Level
 (CEGL) Documents (NRC 1986).  The 24-hour
 EEGL for a carcinogen is estimated as follows:
EEGL  =
d x 25.600 x
   2.8
                              R
                          level of risk at d
 where:

 d    .   =  lifetime   exposure   level   (air
            concentration),  as  computed by  a
            regulatory  agency or  by the NRC
            Committee   on   Toxicology   in
            accordance with procedures used by
            regulatoryagencies (multistage model)
            associated with "acceptable" level of
            cancer risk, e.g., IxlO"6 level of risk,

 25,600  =  number of days in a lifetime  (25,600
            days = 70 years); application of this
            duration   factor   assumes   that
            carcinogenic  effects  are  a  linear
            function  of the  total (cumulative)
            dose,

 2.8      =  a factor to account  for uncertainties
            regarding    which   stage   of
            carcinogenesis   is affected by  the
            substance and for the likely youth of
            military personnel; the NRC  (1986)
            states  that  "the  maximal  additional
            risk   that   these   considerations
            contribute is a factor of 2.8," based on
            the  "data  of  Crump  and  Howe
            (1984)," and

R      =   target   acceptable risk  level  (e.g.,
            IxlO"4) for one day of exposure.

    The reservations with this method concern the
choice of a higher target  risk level (IxlO'4) in
combination  with  other   assumptions of  this
method,  and the origin of the above uncertainty
factor of 2.8.  The origin of this uncertainty factor
is not explained adequately by NRC (1986), nor is
it apparent in the cited paper (Howe and Crump
1986).
                                              -55-

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                           REFERENCES FOR APPENDIX C
Drew, R.T., Boorman G.A., Haseman J.K., McConnell, E.E., Busey, W.M., Moore J.A. 1983.  The Effect of
Age and Exposure Duration on Cancer Induction by a Known Carcinogen in Rats, Mice, and Hamsters. Toxic.
Appl. PharmacoL 68:120-130.

Crump, K.S., Howe, R.B.  1984. The Multistage Model with a Time-dependent Dose Pattern: Applications
to Carcinogenic Risk Assessment. Risk Analysis 4 (3): 163-176.

National Institute of Occupational Safety and Health (NIOSH).  1985.  NIOSH Pocket Guide to Chemical
Hazards. U.S. Department of Health and Human Services.  Washington, DC.

Environmental Protection Agency (EPA). 1986. Guidelines for Carcinogenic  Risk Assessment.  52 Federal
Register 33992.

National Research Council (NRC).  1986. Criteria and Methods for Preparing Emergency Exposure Guidance
Level (EEGL), Short-term Public Emergency Guidance Level (SPEGL), and Continuous Exposure Guideline Level
(CEGL) Documents.  Prepared by the Committee on Toxicology. National Academy Press.  Washington, DC.

Alexeef,  G.V., Lipsett, M.J., and Kizer,  K.W.  1989.  Problems associated with the use of Immediately
Dangerous to Life and Health (IDLH) values for estimating the hazard of accidental chemical releases. Amer.
Ind. Hyg. Assoc. J. 50(11):598-605.

EPA.  1989a. Internal memorandum from J. Cogliano to S. Bayard.  Status of Vinyl Chloride Assessment.
Office of Health and Environmental Assessment.

EPA.   1989b.  Proposed  Amendments to the Guidelines  for the  Health  Assessment  of Suspected
Developmental Toxicants.  45 Federal Register 9386-9403.

American Conference of Governmental and Industrial Hygienists (ACGIH).  1990. Documentation of the
Tftreshold Limit Values and Biological Exposure Indices. Cincinnati, OH.

Agency for  Toxic  Substances and Disease  Registry  (ATSDR).  1991.  Guidance for the Preparation of a
Toxicological Profile.

Howe, R.B.  1991. Personal communication,-telephone conversation with W. Stiteler, Syracuse Research
Corporation, January 30, 1991.
                                               -56-

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                                   APPENDIX  D
  RADIATION REMEDIATION  TECHNOLOGIES
    This appendix presents two exhibits designed
to assist the RPM with the process of using risk
information to evaluate and  select  remediation
technologies   for   sites   contaminated  with
radioactive substances.  The first exhibit, Exhibit
D-l, summarizes the potential routes by which
radioactivity may be released  to  the air, ground
water, surface water, or other media when remedial
technologies are implemented. Similar to Exhibit
A-2 in Appendix A, Exhibit D-l groups process
variations   with    similar   potential  release
mechanisms under  the  technology  categories.
Exhibit  D-l includes ground  and surface water
releases under the "water" column, and includes
other unique release mechanisms under the "other"
column.  The reader is referred to.EPA's report,
Assessment of Technologies for the Remediation of
Radioactivefy   Contaminated   Superfimd  Sites
(EPA/540/2-90/001), for  descriptions  of  each
technology listed in Exhibits D-l and D-2.

    The  second exhibit,  Exhibit D-2, presents a
qualitative  estimate of the  potential short-term
risks  posed  by  each  technology  during  its
implementation phase, and its potential long-term
risks anticipated after cleanup.  Potential short-
term  risks and potential  long-term  risks  are
classified as being low, moderate, or high, or some
combination of these levels.  This classification
scheme  is based on the potential for releases of
radioactivity arising from  the  use  of these
technologies to lead to potential short- and long-
term risks.  Under this scheme, "low" means a low
potential for releases of radioactivity assuming a
reasonable worst-case scenario and therefore, a low
potential for human health or environmental risk.
"Moderate" means a moderate potential for release
and risk, and "high"  refers to a high potential for
release and risk.
    Although the determinations of low, moderate,
and high potential risks presented in Exhibit D-2
are  based  on  the  professional  judgment of
experienced risk assessors, they are provided only
to the RPMs for making preliminary technology
screening decisions.   The actual risks associated
with a remedial alternative at a specific site must
be evaluated on a case-by-case basis.  That is,
technologies rated as high potential risk should not
necessarily be eliminated from consideration, nor
should technologies rated as low potential risk be
considered safe, without evaluation of site-specific
factors.

    The   Agency   recognizes   that   other
determinations of degree of potential risks are
possible  and may  be acceptable.   (In  fact,  if
remediation  technologies are  properly designed
and excuted, few, if any, of the potential releases
and risks may be expected.)  Therefore, the RPM
is encouraged to consider all qualified sources of
technical information when selecting a radiation
remedial  technology  based   on   site-specific
conditions.

    Potential releases of mixed radioactive and
nonradioactive hazardous  substances are  not
covered in this appendix due to the limited number
of  technologies  currently  available,  and  the
complexities   involved   in  identifying  release
pathways and mechanisms.  Because releases of
mixed waste contaminants will warrant additional
risk evaluation and considerations, RPMs should
consult with a radiation protection specialist prior
to selecting a remedial design for these types of
sites.
                                              -57-

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                                                      EXHIBIT D-l

                      POTENTIAL RELEASES OF RADIOACTIVITY ASSOCIATED WITH
                                  RADIATION REMEDIATION TECHNOLOGIES
     Technologies*
             Air
                                             Water*
                                                                                                          Other*
SOIL AND SLUDGE TECHNOLOGIES
Natural Attenuation
(Non-treatment Action)
• Potential emissions of
  radioactive particulates and
  volatiles
• Continued migration of radionuclides
  to ground water and possible transport
  to surface water
• External radiation exposure due to
  gamma-emitting radionuclides in
  soil
Soil Handling
Soil Excavation,
Transport, and Offsite
Disposal
• Resuspension of radioactive
  particulates

• Enhanced emissions of volatile
  radionuclides
• Enhanced runoff or leaching of
  radionuclides to surface water or
  ground water
• Seepage/runoff to soil

• Enhanced external radiation
  exposure of workers during
  excavation, handling, shipping, and
  disposal

• Offsite migration of radioactivity
  due to transport by contaminated
  vehicles or equipment
Soil Washing, Extraction, & Bioremediation
Soil Washing with Water
• Resuspension of radioactive soil
  particles and enhanced
  emissions of volatile
  radionuclides during handling
  and treatment
• Spills, leaching, and/or runoff of
  residual radionuclides in washed soil
  or in process water

• Accumulation of dissolved or
  suspended radionuclides in recycled
  water/solvents
• Enhanced external radiation
  exposure from gamma-emitting
  radionuclides in soil  .
                                                          (Continued)

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                EXHIBIT D-l (Continued)

POTENTIAL RELEASES OF RADIOACTIVITY ASSOCIATED WITH
       RADIATION REMEDIATION TECHNOLOGIES
Technologies'
Air
Water*
Other*
Soil Washing, Extraction, & Bioremediation (Continued)
Chemical Extraction
Bioremediation
• Potential emissions of volatile
chemicals and radioactive
participates and volatiles during
handling and treatment
1
• Areal or fugitive emissions of
radioactive particulates and
volatiles
• Exhaust stack emissions of
incinerated biosorbants
containing residual radioactivity
• Spills, leaching, and/or runoff of
residual radionuclides in process
water
• Accumulation of dissolved or
suspended radionuclides in recycled
water/solvents
• Discharge of process water
containing residual radioactivity
• Inadvertent spills or leaching of
radionuclides
Immobilization
Capping
• Continued emissions of some
volatile radionuclides after
capping
• Leaching and horizontal migration of
radionuclides to ground water with
rain water infiltration ,
• Spills or leakage of extract with
high concentrations of radioactive
contaminants and solvents from
storage tanks
• External radiation exposure from
biomass containing residual
gamma-emitting radionuclides

• Partial reduction of external
radiation exposure
                      (Continued)

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                                                EXHIBIT D-l (Continued)

                       POTENTIAL RELEASES OF RADIOACTIVITY ASSOCIATJ
                                   RADIATION REMEDIATION TECHNOLOGIES
                                                                         WITH
     Technologies*
             Air
              Water*
             Other*
In-situ Vitrification
• Volatilization of certain
  radionuclides during treatment

• Cracks or fissures in vitrified
  mass may act as conduits for the
  release of volatile radionuclides
• Possible leaching and migration of
  radionuclides to ground water due to
  soil matrix destabilization
• .External radiation exposure in
  radium contaminated soils due to
  the buildup of radon decay
  products
GROUND WATER AND SURFACE WATER TECHNOLOGIES
Natural Attenuation
(Non-treatment Action)
• Potential buildup of volatile
  radionuclides (eg, radon) in
  ground-water and municipal
  water distribution systems
• Continued transport of radionuclides
  to the aquifer and possible discharge
  to surface water
• Potential deposition of radioactive
  sediments in surface water over
  large areas (eg, river basins)
Filtration
• Fugitive emissions of volatile
  radionuclides
• Discharge of effluent water containing
  dissolved radioactive solids
• Potential leaching of radionuclides
  from filter cakes or sludge

• External radiation exposure from
  radioactive cakes or sludge
Granular Activated
Carbon Adsorption
• Potential stack emissions of
  volatile radionuclides upon
  saturation or breakthrough
• Discharge of treated water containing
  residual radioactive contamination

• Possible release of radionuclides due
  to backflushing and/or regeneration
• Potential external radiation
  exposure due to the sorption and
  buildup of gamma-emitting
  radionuclides
Ion Exchange
• Potential for off-gassing of
  volatile radioactive decay
  products from parent nuclides
  on resin columns
• Discharge of treated water containing
  residual radioactive contamination

• Possible release of radionuclides due
  to backflushing or regeneration
• Potential external radiation
  exposure due to the buildup of
  gamma-emitting radionuclides
                                                           (Continued)

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                                                 EXHIBIT D-l (Continued)

                        POTENTIAL RELEASES OF RADIOACTIVITY ASSOCIATED WITH
                                    RADIATION REMEDIATION TECHNOLOGIES
NOTES

  * Source for radiation remediation technologies:  US Environmental Protection Agency (EPA).  1990. Assessment of Technologies for the Remediation of
  Radioactively Contaminated Superfund Sites. EPA/540/2-90/001.

  a In general, seepage and leaching are more likely to affect ground water, but could also lead to surface water contamination. Runoff and discharge are
  releases that will most likely contaminate surface water, but may also lead to ground-water contamination.

  b Other releases include treatment residuals requiring further remediation and/or special handling and disposal considerations. External radiation exposure
  due to the presence of gamma-emitting radionuclides in treatment residues should also be considered as a potential human health exposure pathway, even
  though this pathway does not involve the physical release of radionuclides into the environment. The risk assessor should also consider other common
  technologies used to remediate ground water and surface water contaminated with radioactive substances, such as aeration, evaporation, distillation and
  solvent extration, not included in Exhibits D-l or D-2.                                                             *

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                         EXHIBIT D-2
DEGREE OF POTENTIAL SHORT- AND LONG-TERM RISKS ASSOCIATED WITH
             RADIATION REMEDIATION TECHNOLOGIES
Technologies*
Potential for
Short-term Risks
Potential for
Long-term Risks
Comments
SOIL AND SLUDGE TECHNOLOGIES
Natural Attenuation
(Non-treatment
Action)
High
High
• The No Action alternative will not meet the two NCP threshold criteria: (1)
protection of human health and environment, and (2) compliance with ARARs
• Migration and release of radioactive contaminants would be expected to continue
unless abated or mitigated
Soil Handling
Soil Excavation,
Transport, and Offsite
Disposal
Moderate/High
None/Low
• During excavation, the potential for short-term radiation risks to remedial workers
onsite and to the general public.ofisite may be moderate to high
• Once the source or sources of radioactivity has or have been removed, the
potential for long-term risks should be minimal or non-existent, depending on the
level of residual radioactivity remaining onsite
Soil Washing, Extraction, & Bioremediation
Soil Washing with
Water
Chemical Extraction
Moderate
Moderate/High
Low
Low/Moderate
• During excavation and soil washing, the potential for short-term radiation risks to
remedial workers onsite and to the general public offsite may be moderate
• Depending on the level of residual radioactivity remaining, the potential for long-
term risks may be low to moderate
• During excavation and chemical extraction, the potential for short-term radiation
risks to workers onsite and to the general public offsite may be moderate to high
• The potential for long-term risks depend upon the chemical and radiological
characteristics of the treated soil recycled back into native soil
                           (Continued)

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                                                 EXHIBIT D-2 (Continued)

              DEGREE OF POTENTIAL SHORT- AND LONG-TERM RISKS ASSOCIATED WITH
                                    RADIATION REMEDIATION TECHNOLOGIES
  Technologies*
  Potential for
  Short-term
     Risks
 Potential for
  Long-term
    Risks
                                                                                    Comments
 Soil Washing, Extraction, & Bioremediation (Continued)
 Bioremediation
   Moderate
                                   Moderate
                                 • Accidental spillage of radioactivity from biotreatment solutions, off-gassing of volatile
                                   radionuclides, and elevated external radiation exposures may contribute to the potential for
                                   moderate short-term radiation risks

                                 • Long-term risks depend upon the chemical and radiological characteristics of the treated
                                   soil recycled back into native soil In general, these risks should be low to moderate
Immobilization
Capping
Low/Moderate
Moderate/High
• Short-term radiation risks to workers and offsite populations should be low to moderate,
  provided that the source or sources of radioactivity are not excavated before capping

• Since the sources of radioactivity will be left in place, long-term risks to human health and
  the environment may be moderate to high depending on the extent to which the cap is
  capable of preventing the migration of radionuclides in the future
In-situ
Vitrification
Moderate/High
  Moderate
• Initially, both radiation and physical hazards contribute to the moderate to high potential
  for short-term radiation risks posed by the use of this technology, primarily to onsite
  workers                                              •       '          •

• Since the stability and long-term integrity of vitrified soils containing radioactive materials
  remain unverified in the field at the present time, and since the buildup of radon decay
  products in vitrified soils may increase external exposure rates with time, potential long-
  term radiation risks to the general public may be moderate to high
                                                          (Continued)

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I
                                                                      EXHIBIT D-2 (Continued)

                                    DEGREE OF POTENTIAL SHORT- AND LONG-TERM RISKS ASSOCIATED WITH
                                                         RADIATION REMEDIATION TECHNOLOGIES
                         Technologies*
Potential for
 Short-term
   Risks
Potential for
- Long-term
   Risks
                                                                                                         Comments
                        GROUND WATER AND SURFACE WATER TECHNOLOGIES
                        Natural
                        Attenuation
                        (Non-treatment
                        Action)
    High
    High
• The No Action alternative will not meet the two NCP threshold criteria: (1) protection of
  human health and environment, and (2) compliance with ARARs

• Releases of radioactive contaminants to ground water and surface water would be
  expected to continue unless abated or mitigated	
                        Filtration
Low/Moderate
                                                             Low
               • The potential for short-term radiation risks to workers and the public will depend on a
                 number of factors, including: (1) the concentrations of radionuclides in the ground or
                 surface waters; (2) the efficiencies of filtration systems; (3) the breakthrough time, and;
                 (4) the change-out or regeneration cycle time In general, these potential risks are
                 expected to be low to moderate

               • The potential for long-term risks will also depend on the factors listed above, but will
                 depend primarily on the concentration of radionuclides in ground water or surface water
                 remaining to be treated (ie, concentrations (and risks) may be expected to fall off with
                 treatment) Potential risks to the general public may be expected to be low  The handling
                 and disposal of filter materials and sludges containing radionuclides may pose risks to
                 workers if radioactivity  concentrations exceed federal or state standards	
                                                                                 (Continued)

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                                                                EXHIBIT D-2 (Continued)
o
I
DEGREE OF POTENTIAL SHORT- AND LONG-TERM RISKS ASSOCIATED WITH
                     RADIATION REMEDIATION TECHNOLOGIES
i
  'fe
                   Technologies*
     Potential for
      Short-term
        Risks
Potential for
 Long-term
   Risks
                                                                                                  Comments
                 GROUND WATER AND SURFACE WATER TECHNOLOGIES
                 Granular
                 Activated Carbon
                 Adsorption
                 Ion Exchange
    Low/Moderate
    Low/Moderate
   Low
   Low
1 The buildup of radon and radon progeny on activated charcoal may increase both
 potential short- and long-term risks of external radiation exposures to workers
 Regeneration of GAG may release radionuclides that are not well sorbed  Disposal of
 spent GAG containing elevated concentrations of lead-210 (and chemical contaminants)
 may pose handling problems Buildup of radon and other radionuclides on GAG also
 depends on: (1) the concentrations of radionuclides in the ground or surface waters; (2)
 collection efficiencies; (3) GAG breakthrough time, and; (4) the change-out or
 regeneration cycle time
 Similar to the potential risks posed by the treatment of radionuclides in ground water and
 surface water using filtration or carbon absorption techniques, the potential for short- and
 long-term risks posed by the collection of radionuclides on ion exchange resins depends
 primarily on the radionuclide-specific collection efficiency and water concentrations In
 general, these potential risks may be low to moderate
                 * Source for radiation remediation technologies:  U.S. Environmental Protection Agency (EPA).  1990. Assessment of Technologies for the Remediation of
                 Radioactively Contaminated Superfund Sites. Office of Solid Waste and Emergency Response.  EPA/540/2-90/001.                       '

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