United States
Environmental Protection
Agency
Office of Solid Waste and
Emergency Response
Washington, D.C. 20460
Publication 9285.7-01CFS
December 1991
Risk Assessment Guidance
for Superfund: Volume I --
Human Health Evaluation
Manual (Part C)
Office of Emergency and Remedial Response
Hazardous Site Evaluation Division, OS-230
Quick Reference Fact Sheet
The overarching mandate of the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA) program is to protect human health and the environment from current and potential threats posed
by uncontrolled releases of hazardous substances. To help meet this mandate, the U.S. Environmental
Protection Agency's (EPA's) Office of Emergency and Remedial Response (OERR) has developed a human
health evaluation process as part of its remedial response program. EPA's Human Health Evaluation Manual,
which describes the process of gathering information and assessing the risk to human health, and the
Environmental Evaluation Manual comprise a two-volume set (Volumes I and II, respectively) called Risk
Assessment Guidance for Superfund (RAGS). RAGS replaces two previous EPA guidance documents: the
Superfund Public Health Evaluation Manual (SPHEM; 1986) and the Draft Endangerment Assessment Handbook
(1985).
The Human Health Evaluation Manual (HHEM) has three main parts: Pan A, which discusses the baseline
risk assessment; Pan B, Development of Risk-based Preliminary Remediation Goals; and Pan C, Risk Evaluation
of Remedial Alternatives. Because Part A contains detailed guidance on risk assessment activities such as data
evaluation, exposure assessment, toxicity assessment, and risk characterization, it is necessary background for
many of the evaluations discussed in Parts B and C. This fact sheet is designed to introduce remedial project
managers (RPMs) and other personnel to the risk evaluation of remedial alternatives and to the information
that is available in RAGS/HHEM Part C. RPMs should ensure that these procedures are used whenever
considering human health risks of remedial alternatives.
OVERVIEW OF PART C:
EVALUATING RISKS OF REMEDIAL
ALTERNATIVES
Part C assists RPMs, risk assessors, site engineers,
and others in using human health risk information
to evaluate remedial alternatives. Part C discusses
how to evaluate the long-term risks (i.e., residual
risks) and short-term risks (i.e., risks during
remedy implementation) associated with remedial
alternatives. It also provides appendices with more
detailed information about the types of releases
expected from remedial technologies and about
short-term toxicity values. Some consideration of
risk is inherent during the remedial investigation/
feasibility study (RI/FS) and during activities that
follow the RI/FS, including development of the
proposed plan and record of decision (ROD),
remedial design, remedy implementation, and five-
year review. Risk evaluation of remedial
alternatives is part of the overall FS process, as
described in Guidance for Conducting Remedial
Investigations and Feasibility Studies Under
CERCLA (EPA 1988). Highlight 1 illustrates the
relationship between the CERCLA process and the
risk evaluations of remedial alternatives; Highlight
2 summarizes the risk evaluations of remedial
alternatives that take place.
The level of effort for risk evaluations of remedial
alternatives is typically lower than for the baseline
risk assessment and depends primarily on the site-
specific questions that must be answered to select
and implement a remedy that will be protective of
human health. For many sites, a qualitative
evaluation of the risks associated with remedial
alternatives will be appropriate. For other sites, a
more quantitative evaluation of risks may be
needed. For example, if the relative residual risk
associated with each remedial alternative (e.g., W6,
10~5, 10"4) is an important factor in selecting an
alternative, a more detailed evaluation of long-
term risks may be needed. If the releases
-------
Highlight 1
RISK EVALUATION OF REMEDIAL ALTERNATIVES IN THE^UPERFUND PROCESS
STAGES IN REMEDIATION
Remedial
Investigation
Feasibility
Study
Selection of
Remedy
Remedial Design/
Remedial Action
Deletion/
Five-year Review
STAGES IN EVALUATING REMEDIAL ALTERNATIVES
Evaluate Attainment of
Final Goals and
Residual Risk
associated with implementation of a remedial
alternative are not well-characterized or if
residential populations are located nearby, a more
detailed evaluation of short-term risks may be
needed. Highlight 3 lists additional factors to
consider when determining the appropriate level of
effort. Part C contains two case study examples
that illustrate a qualitative and a quantitative risk
evaluation of remedial alternatives.
EVALUATING LONG-TERM RISKS
What are long-term risks?
Long-term risks are those risks that remain after a
remedial action is completed. Evaluating long-
term risks involves considering the residual risk
associated with an alternative and the ability of the
alternative to maintain protection over time.
How are long-term risks evaluated?
The evaluation of residual risk typically involves a
comparison of the concentrations a remedy has
attained or is predicted to attain in an
environmental medium with concentrations
deemed by EPA to be protective of human health.
In addition to this comparison, the ability of a
remedy to maintain protection over time should be
evaluated for alternatives that involve engineering
or institutional controls. Failure of such controls
could result in increased long-term risks, and
therefore the likelihood of remedy failure and the
magnitude of risks resulting from such a failure
should be considered.
When are long-term risks evaluated?
Long-term risks should be evaluated at several
points in the CERCLA process, including the:
FS (screening and detailed analysis);
proposed plan and ROD;
remedial design;
remedy implementation; and
five-year reviews.
Most of the long-term risk evaluation will be
conducted during the detailed analysis of the FS;
however, additional information (e.g., treatability
studies) may become available later and the
evaluations performed during the FS may be
revised. The long-term risks then must be
documented in the ROD. During remedy
-------
Highlight 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
Risk0
Qualitative
Qualitative or
Quantitative11
Qualitative or
Quantitative*1
Qualitative or
Quantitative"1
Qualitative or
Quantitative"1
Quantitative
Generally not
applicable
Long-term
Risk
Qualitative
Qualitative or
Quantitative"1
Qualitative or
Quantitative11
Qualitative or
Quantitative"1
Qualitative or
Quantitatived
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 Part C and Highlight 3 of this fact sheet 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 Part C for additional information.
' Short-lerm risk refers to risks that occur during remedy implementation.
ms lor ckvuJini; whether ;i qualitative or quantitative risk evaluation is needed for these stages.
-------
Highlight 3
FACTORS TO CONSIDER WHEN
DECIDING WHETHER 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;
use of an onsite incinerator;
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.
implementation, evaluation of long-term risks
involves assessing attainment of the remediation
goals. During five-year reviews, evaluation of long-
term risks ensures that the remedy remains
protective of human health.
EVALUATING SHORT-TERM RISKS
What are short-term risks?
The short-term risks associated with a remedial
alternative are those risks that occur during
implementation of the alternative. Because some
remedies may take many years to complete, some
"short-term" risks may actually occur over a
relatively long period of time. The populations
that may be subject to short-term risks are (1)
people who live or work in the vicinity of the site
and (2) workers who are involved in site
remediation.
How are short-term risks evaluated?
Evaluating short-term risks involves the same basic
steps as the baseline risk assessment: exposure
assessment, toxicity assessment, and risk
characterization. These steps generally are
conducted in a less quantitative manner than for
the baseline risk assessment, however. Highlight 4
provides a summary of some of the differences
between the baseline risk assessment and the
assessment of short-term risks of remedial
alternatives. Part C discusses both qualitative and
quantitative evaluation of these short-term risks.
When are short-term risks evaluated?
Short-term risks should be evaluated at several
times during the selection and implementation of
a remedial alternative, including:
FS (screening and detailed analysis);
proposed plan and ROD;
remedial design; and
remedy implementation.
Because the short-term risks associated with .ğ
remedial alternative are a consideration m
selecting an alternative, most of the analysis "I
short-term risks should be conducted durme (he
FS, and the risks associated with the selected
alternative should be documented in the ROD
During design of the remedy, previous i,-k
evaluations may be refined, as needed. .mĞi
engineering controls or other measures to mm-Mie
-------
Highlight 4
BASELINE RISK ASSESSMENT AND
RISK EVALUATION 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 by 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 (Part 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
action).
Characterize Risks (Part A - Chapter 8)
A risk evaluation of remedial alternatives
generally considers risks to on-site workers, as
well as risks to the surrounding community.
Additional uncertainties (e.g., predicting
releases from remediation technologies) exist.
risks may be identified. If potential risks to the
community are a concern or there is high
uncertainty regarding these predicted risks, a
strategy to monitor exposure concentrations during
remedy implementation should be developed.
USING PART C APPENDICES
Part C includes four appendices that contain useful
information for evaluating the risks associated with
remedial alternatives.
Appendix A: Selected Remediation Technologies
and Associated Potential Releases. Appendix A
contains two exhibits designed to assist in
identifying some of the potential releases that are
associated with commonly used remedial
technologies. Exhibit A-l describes each process
option for the technologies included in Exhibit
A-2. Exhibit A-2 summarizes the releases to air
and water and the treatment residuals associated
with common remediation technologies.
Appendix B: Quantifying Potential Releases from
Selected Remediation Technologies. Appendix B
provides more detailed descriptions of the releases
associated with several common remediation
activities and examples of the considerations
involved in quantifying technology-specific releases.
It also contains lists of references that provide
information on quantifying releases for soils
handling, thermal destruction, and
stabilization/solidification technologies, as well as
references that pertain to a variety of remediation
technologies.
Appendix C: Short-term Toxicity Values.
Appendix C provides general background on
exposure duration, a summary of existing short-
term human health toxicity values, and information
on where to obtain short-term toxicity values.
Short-term toxicity values have been developed by
a number of agencies and programs, and some of
these values are not appropriate for use in
characterizing risks associated with remedial
alternatives. Therefore, EPA staff must call the
Superfund Health Risk Technical Support Center
(TSC) at FTS 684-7300 (513/569-7300) whenever
short-term risks are to be characterized. The TSC
will maintain an up-to-date database for these
toxicity values.
Appendix D: Radiation Remediation Technologies.
Appendix D contains two exhibits designed to
assist in the process of using risk information to
evaluate remediation technologies for sites
-------
contaminated with radioactive substances. Exhibit
D-l summarizes the potential releases of
radioactivity associated with a number of
remediation technologies. Exhibit D-2 presents a
qualitative estimate of the potential short-term and
long-term risks associated with selected radiation
remediation technologies.
RPM INVOLVEMENT
The RPM needs to have a comprehensive
understanding of the risk evaluation of remedial
alternatives in order to make decisions for risk
management purposes. Part C includes a list of
questions for RPMs on risks of remedial
alternatives (presented in Highlight 5) and
guidance on documenting the risk evaluations of
remedial alternatives at appropriate points in the
CERCLA process.
Highlight 5
QUESTIONS RPMs SHOULD ASK
ABOUT THE RISKS OF
REMEDIAL ALTERNATIVES
Which alternatives will clearly not address the
significant human exposure pathways
identified in the baseline risk assessment?
Which technologies can readily achieve PRGs
in a given medium? What uncertainties are
associated with this determination?
Are the expected residual risks from one
alternative significantly different from
another?
What other risk-based benefits are there in
selecting one alternative over another?
Will implementation of specific technologies
create significant exposures or risks for the
surrounding community?
Is there a need for engineering controls or
other measures to mitigate risks? Are such
controls available, and what is their
reliability?
Does the remedial action result in hazardous
substances remaining at the site such that
five-year reviews are required?
NEED MORE HELP?
Regional Toxics Integration Coordinators
Regional Toxics Integration Coordinators
(Highlight 6) can provide additional information
concerning the risk evaluations of remedial
alternatives.
Superfund Health Risk Technical Support Center
Regional EPA CERCLA staff must contact the
Superfund Health Risk Technical Support Center
of the Environmental Criteria and Assessment
Office (ECAO) at FTS 684-7300 (513/569-7300)
for guidance on short-term toxicity criteria.
Requests for information from other users must be
submitted in writing to the TSC and provide:
CERCLA site name, site location, and 12-
digit site number;
name and phone number of the site RPM;
and
detailed description of the risk assessment
related question.
Risk Reduction Engineering Laboratory
Risk Reduction Engineering Laboratory (RREL;
Cincinnati, Ohio) personnel can provide site-
specific technical services involving a variety of
treatment technologies and Superfund response
processes. Regional EPA CERCLA staff should
direct questions regarding evaluations of and
previous experience with remediation technologies
and releases associated with remediation
technologies to the Engineering and Treatment
Technical Support Center at FTS 684-7406
(513/569-7406).
Where to Obtain Copies
EPA staff can obtain copies of Part C or additional
copies of this fact sheet by calling EPA's Center
for Environmental Research Information at FTS
684-7562 (513/569-7652). Others can obtain copies
by contacting NTIS at 800/336-4700 (703/487-4650
in the Washington, DC area).
-------
Highlight 6
SUPERFUND REGIONAL TOXICS INTEGRATION COORDINATORS
EPA Region
Toxics Integration Coordinator
Telephone
10
Sarah Levinson
John F. Kennedy Federal Bldg.
Boston, MA 02203
Peter Grevatt
26 Federal Plaza
New York, NY 10278
Dr. Richard Drunker
841 Chestnut Street
Philadelphia, PA 19107
Dr. Elmer Akin
345 Courtland Street, NE
Atlanta, GA 30365
Erin Moran
230 S. Dearborn Street
Chicago, IL 60604
Jon Rauscher
First Interstate Bank Tower
1445 Ross Avenue
Dallas, TX 75202
Dave Crawford
726 Minnesota Avenue
Kansas City, KS 66101
Chris Weis
999 18th Street, Suite 500
Denver, CO 80202
Dan Stralka
75 Hawthorne Street
San Francisco, CA 94105
Pat Cirone
1200 6th Avenue
Seattle, WA 98101
FTS 833-1504
617/223-5504
FTS 264-6323
212/264-6323
FTS 597-0804
215/597-0804
FTS 257-1586
404/347-1586
FTS 353-1420
312/353-1420
FTS 255-2198
214/655-2198
FTS 276-7702
913/551-7702
FTS 330-7655
303/294-7655
FTS 484-2310
415/744-2310
FTS 399-1597
206/553-1597
------- |