Download version 0.1 of EM 200-1-4 Risk Assessment Handbook Volume 1 Human Health Evaluation.pdf

Download version 0.1 of EM 200-1-4 Risk Assessment Handbook Volume 1 Human Health Evaluation.pdf
CEMP-RT
Department of the Army
EM 200-1-4
U.S. Army Corps of Engineers
Engineer Manual
200-1-4
Washington, DC 20314-1000
Environmental Quality
RISK ASSESSMENT HANDBOOK
VOLUME I:
HUMAN HEALTH EVALUATION
Distribution Restriction Statement
Approved for public release; distribution is
unlimited.
31 January 1999
EM 200-1-4
31 January 1999
ENVIRONMENTAL QUALITY
RISK ASSESSMENT HANDBOOK
VOLUME I: HUMAN HEALTH
EVALUATION
ENGINEER MANUAL
This Engineer Manual is approved for public release, distribution is unlimited.
AVAILABILITY
Electronic copies of this and other U.S. Army Corps of Engineers (USACE) publications are
available on the Internet at http://www.usace.army.mil/inet/usace-docs/. This site is the only
repository for all official USACE engineer regulations, circulars, manuals, and other
documents originating from HQUSACE. Publications are provided in portable document
format (PDF).
DEPARTMENT OF THE ARMY
U. S. Army Corps of Engineers
Washington, D.C. 20314-1000
CEMP-RT
Manual
No. 200-l-4
EM 200-l -4
3 1 January 1999
Environmental Quality
RISK ASSESSMENT HANDBOOK
VOLUME I: HUMAN HEALTH EVALUATION
1. Purpose. The overall objective of this manual is to provide risk assessorswith the recommended
basic/minimum requirements for developing scopes of work, evaluating Architect-Engineer (A-E) prepared human
health risk assessments, and documenting risk management options associated with Hazardous, Toxic, and
Radioactive Waste (HTRW) investigations, studies, and designs consistent with principles of good science in
defining the quality of risk assessments. This EM is intended for use by U.S. Army Corps of Engineers (USACE)
Project Managers, technical personnel, and contractor personnel.
2. Applicability.
projects.
This EM applies to all HQUSACE elements and USACE commands responsible for HTRW
3. References. References are listed in Appendix A.
4. Distribution.
Approved for public release, distribution is unlimited.
5. Discussion. This manual is intended to provide USACE risk assessorsand contractor personnel with
supplemental guidance for performance and evaluation of risk assessmentsunder the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA) as amended by the Superfund Amendments and
Reauthorization Act (SARA) of 1986, and the Resource Conservation and Recovery Act (RCRA) as amended by
the Hazardous and Solid Waste Amendments (HSWA) of 1984. It is not intended to replace the accepted guidance
by the USEPA (e.g., Risk Assessment Guidance for Superfund, Human Health Evaluation Manual), but should be
used in conjunction with that document. Additional information provided by this manual concerns presentation of
the risk assessment results for use in risk management and decision-making, concerns focusing on the decisions, and
criteria needed for decisions. Both risk and nonrisk factors are presented for consideration by the risk managers.
FOR THE COMMANDER:
2 Appendices
(See Table of Contents)
Major General, USA
Chief of Staff
This manual supersedes EM 200-I-4, Volume I, dated 30 June 1995.
@Printed on Recycled Paper
CEMP-RT
Manual
No. 200-1-4
DEPARTMENT OF THE ARMY
U.S. Army Corps of Engineers
Washington, D.C. 20314-1000
EM 200-1-4
31 January 1999
Environmental Quality
RISK ASSESSMENT HANDBOOK, VOLUME I: HUMAN HEALTH EVALUATION
Table of Contents
Chapter
Page
1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . 1-1
1.1 PURPOSE AND SCOPE . . . . . . . . . . . . . . 1-1
1.1.1
Objectives. . . . . . . . . . . . . . . . . . . 1-1
1.1.2
Scope. . . . . . . . . . . . . . . . . . . . . . . 1-1
1.1.3
Intended Audience and Use. . . . . 1-2
1.1.4
Contents of the Handbook. . . . . . 1-2
1.2 USACE ROLE IN THE HTRW PROGRAM
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.2.1
DERP. . . . . . . . . . . . . . . . . . . . . . 1-3
1.2.2
BRAC. . . . . . . . . . . . . . . . . . . . . . 1-3
1.2.3
Others. . . . . . . . . . . . . . . . . . . . . . 1-3
1.2.4
HTRW Program Organization. . . 1-4
1.3 OVERVIEW OF HTRW RESPONSE
PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
1.3.1
CERCLA Process. . . . . . . . . . . . . 1-4
1.3.2
RCRA Corrective Action Process. 1-6
1.3.3
Functional Equivalency of the
CERCLA and RCRA Processes. . 1-7
1.3.4
Role of Risk Assessment in the HTRW
Process. . . . . . . . . . . . . . . . . . . . . 1-7
1.4 CONCEPT OF RISK ASSESSMENT AND
GOOD SCIENCE . . . . . . . . . . . . . . . . . . . 1-11
1.4.1
Basic Concepts. . . . . . . . . . . . . . 1-12
1.4.2
Risk Assessment as Decision Criteria
in the HTRW Program. . . . . . . . 1-12
1.5 POLICY CONSIDERATIONS AND RISK
MANAGEMENT . . . . . . . . . . . . . . . . . . . 1-12
1.5.1
Relationship Between Policy
Considerations and Risk. . . . . . . 1-13
1.5.2
USACE Policy Considerations . 1-13
1.5.3
EPA Headquarters, Regional and State
Policies. . . . . . . . . . . . . . . . . . . . 1-14
1.5.4
Risk-Based Management Decisions for
Site Actions. . . . . . . . . . . . . . . . . 1-14
1.6 REGULATORY DIRECTIVES AND
GUIDANCE . . . . . . . . . . . . . . . . . . . . . . . 1-14
1.6.1
EOs and Federal Statutes/Regulations
. . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
1.6.2
DOD Directives. . . . . . . . . . . . . 1-16
Chapter
Page
1.6.3
EPA Headquarters and Regional
Guidance. . . . . . . . . . . . . . . . . . . 1-16
1.6.4
State Requirements/Guidance. . 1-18
1.6.5
Others. . . . . . . . . . . . . . . . . . . . . 1-18
1.7 FEDERAL FACILITY AGREEMENT . . 1-19
1.7.1
Basis for Interim Remedial Action
(IRA) Alternatives. . . . . . . . . . . 1-20
1.7.2
Requirements for RI/RFI and FS/CMS
. . . . . . . . . . . . . . . . . . . . . . . . . . 1-20
1.7.3
Expedited Cleanup Process. . . . 1-20
1.7.4
Units Excluded from the Agreement
. . . . . . . . . . . . . . . . . . . . . . . . . . 1-21
2.0 PLANNING FOR AN HHRA . . . . . . . . . . . . 2-1
2.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . 2-1
2.1.1
Purpose of the HHRA. . . . . . . . . . 2-1
2.1.2
Objectives of the HHRA. . . . . . . . 2-1
2.1.3
Minimum Requirements. . . . . . . . 2-1
2.1.4
Technical Requirements. . . . . . . . 2-2
2.1.5
Technical Basis. . . . . . . . . . . . . . . 2-2
2.1.6
Planning and Problem Identification
. . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.2 PLANNING CONSIDERATIONS . . . . . . 2-3
2.2.1
Coordinating HHRA and ERA
Planning. . . . . . . . . . . . . . . . . . . . 2-3
2.2.2
Coordination with Natural Resource
Trustees . . . . . . . . . . . . . . . . . . . . 2-4
2.2.3
RAGS, Part D: Standardized Planning,
Reporting, and Review of Superfund
Risk Assessments . . . . . . . . . . . . 2-4
2.2.4
The HTRW TPP Process. . . . . . . 2-5
2.3 ESTABLISHING THE LEVEL OF EFFORT
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
2.3.1
Preliminary Risk Screening; PA/SI
. . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
2.3.2
HHRA; RI. . . . . . . . . . . . . . . . . . . 2-9
2.3.3
Risk-Based Analysis of Remedial
Alternatives; FS. . . . . . . . . . . . . 2-13
i
EM 200-1-4
31 Jan 99
Chapter
Page
2.3.4
Short-Term Risks Associated With
Construction. . . . . . . . . . . . . . . . 2-15
3.0 EVALUATING THE SCREENING-LEVEL
HHRA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . 3-1
3.2 SCREENING-LEVEL HHRAs . . . . . . . . . 3-1
3.2.1
Chemical Data Collection and Review
3-1
3.2.2
Exposure Assessment. . . . . . . . . . 3-1
3.2.3
Health-Based Screening Levels. . 3-2
3.2.4
Risk Screening. . . . . . . . . . . . . . . 3-2
3.2.5
Characterization of Uncertainty. . 3-2
4.0 EVALUATING THE BASELINE HHRA . . 4-1
4.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . 4-1
4.2.1
Historical Data Review. . . . . . . . . 4-2
4.2.2
Guidance. . . . . . . . . . . . . . . . . . . . 4-2
4.2.3
Evaluation of Data Quality. . . . . . 4-2
4.3 SELECTION OF COPCs . . . . . . . . . . . . . . 4-3
4.3.1
Objectives. . . . . . . . . . . . . . . . . . . 4-3
4.3.2
General Considerations. . . . . . . . . 4-4
4.3.3
Selection Criteria/Methodology. . 4-4
4.3.4
Presentation of COPCs. . . . . . . . . 4-5
4.4 EXPOSURE ASSESSMENT . . . . . . . . . . 4-5
4.4.1
Refinement of the CSM. . . . . . . . 4-6
4.4.2
Characterization of the Exposure
Setting. . . . . . . . . . . . . . . . . . . . . . 4-6
4.4.3
Identification of Exposure Pathways
and Intake Routes. . . . . . . . . . . . . 4-6
4.4.4
Identification of Potential Receptor
Populations. . . . . . . . . . . . . . . . . . 4-7
4.4.5
Quantitation of Exposure (Intake or
Dose. . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
4.5 TOXICITY ASSESSMENT . . . . . . . . . . 4-10
4.5.1
Objectives. . . . . . . . . . . . . . . . . . 4-10
4.5.2
Derivation of Toxicity Values. . 4-10
4.5.3
Toxicity Assessment for Carcinogenic
Effects. . . . . . . . . . . . . . . . . . . . . 4-10
4.5.4
Toxicity Assessment For
Noncarcinogenic Effects. . . . . . . 4-10
4.5.5
Sources of Toxicity Values. . . . . 4-11
4.5.6
Use of Toxicity Values. . . . . . . . 4-11
4.5.7
Special Chemicals. . . . . . . . . . . . 4-12
4.6 RISK CHARACTERIZATION . . . . . . . . 4-15
4.6.1
Objective. . . . . . . . . . . . . . . . . . . 4-15
4.6.2
Methodology. . . . . . . . . . . . . . . . 4-15
ii
Chapter
Page
4.7 EVALUATION OF UNCERTAINTIES AND
LIMITATIONS . . . . . . . . . . . . . . . . . . . . . 4-16
4.7.1
Objective. . . . . . . . . . . . . . . . . . . 4-16
4.7.2
Sources of Uncertainty. . . . . . . . 4-16
4.7.3
Evaluation of Uncertainty. . . . . . 4-19
5.0 EVALUATING THE HHRA OF REMEDIAL
ALTERNATIVES . . . . . . . . . . . . . . . . . . . . . . 5-1
5.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . 5-1
5.2 DEVELOPMENT OF RGs . . . . . . . . . . . . 5-1
5.3 EVALUATION OF LONG-TERM RISKS 5-2
5.3.1
Comparative Risk Assessment of
Remedial Alternatives. . . . . . . . . 5-2
5.3.2
Risk Reduction. . . . . . . . . . . . . . . 5-2
5.3.3
Residual Risk. . . . . . . . . . . . . . . . 5-2
5.4 SHORT-TERM RISKS ASSOCIATED WITH
REMEDIATION . . . . . . . . . . . . . . . . . . . . 5-2
6.0 RISK MANAGEMENT - INFORMATION
NEEDED FOR DECISION-MAKING . . . . 6-1
6.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . 6-1
6.2 DETERMINING REQUIREMENTS FOR
ACTION . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4
6.2.1
PA/SI and RFA. . . . . . . . . . . . . . . 6-4
6.2.2
RI/RFI. . . . . . . . . . . . . . . . . . . . . . 6-9
6.2.3
FS/CMS and RD/RA. . . . . . . . . 6-11
6.2.4
Non-Risk Issues or Criteria as
Determining Factors for Actions
. . . . . . . . . . . . . . . . . . . . . . . . . . 6-15
6.3 DESIGN CONSIDERATIONS . . . . . . . . 6-18
6.3.1
Potential Risk Mitigation Measures
. . . . . . . . . . . . . . . . . . . . . . . . . . 6-18
6.3.2
Risk Management; Degree of
Protectiveness. . . . . . . . . . . . . . . 6-19
Appendix A. References
Appendix B. Acronyms
A-1
B-1
EM 200-1-4
31 Jan 99
CHAPTER 1
1.0 INTRODUCTION
1.1 PURPOSE AND SCOPE
This handbook, Risk Assessment Handbook: Volume I Human Health Evaluation, provides technical guidance to
the U.S. Army Corps of Engineers (USACE) risk assessors
and risk assessment support personnel for planning,
evaluating, and conducting Human Health Risk
Assessments (HHRAs) in a phased hazardous, toxic, and
radioactive waste (HTRW) response action.
The
handbook, a compendium to the Risk Assessment
Handbook: Volume II - Environmental Evaluation
(Engineer Manual (EM) 200-1-4), encourages the use of
"good science" within the framework of existing U.S.
Environmental Protection Agency (USEPA)
risk
assessment guidelines.
Reference and overview resources:
Required and Related References (Appendix
&
A)
Abbreviations and Acronyms
&
(Appendix B)
Risk characterization is a similar process for both human
health and Ecological Risk Assessments (ERAs). The
fundamental paradigm for human health risk
characterization has four phases: (1) hazard identification,
(2) dose-response assessment, (3) exposure assessment,
and (4) risk characterization. Similarly, the fundamental
framework for ecological risk characterization includes four
phases: (1) problem formulation, (2) ecological effects
characterization, (3) exposure characterization, and (4) risk
characterization.
This handbook encourages the concurrent assessment of
human and ecological risks so that data collection activities
are coordinated and risk managers are provided risk
characterization results in a timely manner. Risk
characterization results for human and ecological receptors
should be reasonable and communicated to the risk
managers in a clear and unbiased manner to facilitate the
making of balanced and informed risk management
decisions.
1.1.1
Objectives. The overall objective of this
handbook is to allow the users to be familiar with the risk
assessment process so that quality data will be collected
and used in preparing a site-specific risk assessment.
Specifically, the objectives are:
&
To provide guidance for all risk assessments
completed under contract with USACE or those for
which USACE provides technical oversight (including
active Installation Restoration Program [IRP] and
Formerly Used Defense Sites [FUDS] and other
Federal agencies/facility sites), in compliance with
Federal environmental laws and regulations.
&
To allow users to be familiar with the application of
the data quality design process with respect to
conducting risk assessments, so that data collected will
support risk assessment conclusions.
&
To highlight those decision criteria specific to each
phase of HTRW project execution that support risk
management decisions.
&
To provide minimum requirements for evaluating
contractor-prepared risk assessments, assuring that the
assessment will adequately support site decisions of an
HTRW response action.
&
To acknowledge areas of uncertainties where "good
science," based on professional judgement and sound
scientific principles, is used to determine the need for
removal actions or interim measures, further
investigation, further action, or no further action
(NFA) needed (site closeout).
&
To refine understanding of EPA's concepts and
application of risk assessment guidelines for site
assessment and remediation, especially to support the
USACE HTRW program goals.
1.1.2
Scope. This guidance document is not intended
to be a "how to" manual which prescribes step-by-step
procedures or instructions for preparing an HHRA. Rather,
it presents recommendations for scoping, managing,
evaluating, and communicating to risk managers and other
stakeholders the potential risks posed by hazardous
Chemicals Of Concern (COCs) at Comprehensive
Environmental Response, Compensation, and Liability Act
(CERCLA) sites, Resource
1-1
EM 200-1-4
31 Jan 99
Conservation and Recovery Act (RCRA) sites, and other
sites managed under the HTRW program. This handbook
provides concepts for performing a risk assessment
consistent with "good science" and accepted regulatory
procedures. The following areas are not covered in this
handbook:
&
Biological hazards - microbes (natural or genetically
engineered) and other biological agents.
&
Radioactive hazards - radioactive wastes, radiation
generating devices, and radioactively contaminated
materials.
&
Lead-based paint and asbestos hazards.
&
Physical hazards - building demolition/debris removal.
&
Study elements and regulatory requirements of a
Natural Resource Damage Assessment.
1.1.3
Intended Audience and Use. This document is
prepared primarily for use by USACE personnel who are
responsible for scoping, directing, and reviewing HHRAs
performed for HTRW response action sites. The guidelines
provided by this document are consistent with and should
be considered in addition to existing EPA guidance
contained in the Risk Assessment Guidance for Superfund
(RAGS), Volume I, Part A (USEPA, 1989j), Part B
(USEPA, 1991d), Part C (USEPA, 1991e), and Part D
(USEPA, 1998a), and Data Usability for Risk Assessments
(USEPA, 1992h). The EM entitled Technical Project
Planning (TPP) Process (EM 200-1-2) (USACE) should
be reviewed, particularly for understanding the process
described in Chapter 2 of this handbook on how to
determine data quality objectives (DQOs) to support a risk
assessment.
The data collection, assessment, characterization of risk
and uncertainty, and the risk management decision-making
(RMDM) aspects presented in this handbook are intended
to satisfy RCRA and CERCLA regulatory requirements.
The assessment of human health risks under these two
functionally equivalent programs is essentially the same. If
both regulatory programs are applicable at a site or unit, the
risk assessment components should be closely coordinated
to avoid duplication of effort. Where possible, the technical
1-2
and risk management approaches should be incorporated
as specific language in agreements with EPA or states.
1.1.4
Contents of the Handbook. Chapter 1 presents
the purpose, scope, concept, science/policy considerations,
and the use of risk assessment in HTRW programs. It
provides a description of the USACE HTRW program,
quality required for performing a risk assessment, and an
understanding of how risk assessments serve management
decision needs. Relevant Federal statutes/regulations,
agency guidance and directives, and state requirements are
highlighted in this chapter.
Chapter 2 presents the major scoping or project planning
elements under CERCLA as amended by the Superfund
Amendments and Reauthorization Act (SARA) of 1986,
and RCRA as amended by the Hazardous and Solid Waste
Amendments (HSWA) of 1984. Particular emphasis is
placed on the early development of a conceptual site model
(CSM) in the data quality design process to identify data
needs, optimize data collection efforts, and recommend
options for site decisions.
Chapter 3 provides an introduction to the HHRA process
as it applies to screening-level assessments. Screeninglevel HHRAs are typically utilized in the Preliminary
Assessment/Site Inspection (PA/SI) or RCRA Facility
Assessment (RFA) stage of site investigations.
Chapter 4 is intended to provide the risk assessor with the
minimum content expected to be included in a Baseline
Risk Assessment (BRA), conducted during the Remedial
Investigation (RI) or RCRA Facility Investigation (RFI)
phase of investigations. This chapter stresses the
importance of properly identifying the Chemicals of
Potential Concern (COPCs) and developing a thorough
understanding of the dynamics or inter-relationships of
multiple pathway exposure models. Appropriate methods
for estimating exposure point concentrations are also
presented. The importance of objectively and realistically
characterizing site hazards or risks is discussed relative to
satisfying the regulatory requirements of protectiveness of
human health and the environment.
Chapter 5 provides the risk assessor with information to
evaluate risk assessments conducted during the Feasibility
Study (FS) or Corrective Measures Study
EM 200-1-4
31 Jan 99
(CMS) and Remedial Design/Remedial Action (RD/RA) or
Corrective Measures Implementation (CMI) phases of
investigations.
For the purpose and intended use of this risk assessment
handbook, the focus is on the DERP and BRAC cleanup
programs to address CERCLA- and RCRA-related issues.
Chapter 6 provides guidance on the risk and uncertainty
aspects of RMDM. Both risk and non-risk information are
collected and presented for consideration by the manager.
This chapter emphasizes balancing the need for protection
of human health with other project constraints, including
the level of confidence and uncertainty in the risk
assessment results. It details approaches for evaluating the
need for NFA, removal (or interim corrective measure),
and remediation. Additionally, Chapter 6 provides the risk
assessment information inputs into the decision criteria and
rationale for the selection of remedial alternatives or
corrective measures. Chapter 6 concludes that the risk
assessor is responsible for presenting key risk information
to be used as input into risk management options including
documentation of uncertainty and rationale.
1.2.1
DERP. DERP, codified in 10 USC Chapter 160,
provides central program management for the cleanup of
DOD hazardous waste sites consistent with the provisions
of CERCLA. The goals of the program are: (1) the
identification, investigation, research, and cleanup of
contamination from hazardous substances; (2) correction of
other environmental damage which creates an imminent
and substantial endangerment to the public health or the
environment; and (3) demolition and removal of unsafe
buildings and structures.
1.2 USACE ROLE IN THE HTRW PROGRAM
In the execution of USACE environmental missions, the
HTRW program is organized and staffed to respond to
assignments for the following national environmental
cleanup programs:
&
EPA Superfund Program (CERCLA)
&
Defense Environmental Restoration Program (DERP):
-
IRP
FUDS
Department of Defense and State Memorandum
of Agreement/Cooperative Agreement Program
(DSMOA/CA)
&
Base Realignment and Closure (BRAC)
&
Environmental Compliance Assessment System
(ECAS) (USACE 1992a)
&
HTRW environmental restoration support for Civil
Works projects and other Federal agencies
(Department of Defense [DOD] and non-DOD)
1.2.2
BRAC. BRAC is an environmental restoration
program with the mission to restore or clean up DOD
installations in preparation of real property disposal or
transfer. The Base Closure Account (BCA) funds the
BRAC program. The BCA is authorized under the Defense
Authorization Amendments and Base Closure and
Realignment Act of 1988 and the Defense Base Closure
and Realignment Act of 1990. These funds are used to
define the nature and scope of contamination, perform RA,
and document the condition of real property by issuance of
the Finding of Suitability to Lease (FOSL) (DOD, 1993)
and the Finding of Suitability to Transfer (FOST) (DOD,
1994a).
The Community Environmental Response
Facilitation Act (CERFA) (Public Law 102-426) amends
CERCLA Section 120(h) and requires Federal agencies to
define "real property" on which no hazardous substances
and no petroleum products or their derivatives were stored
for 1 year or more, were known to have been released, or
were disposed of before the property can be transferred.
Transfer of contaminated property is allowed as long as the
RA to clean up the site is demonstrated to be effective to
EPA.
1.2.3
Others. Other components of the USACE
HTRW program include:
&
EPA Superfund program support - Through an
interagency agreement (IAG) and upon EPA request,
USACE acts as the Federal government's contracting
officer in conducting "Federal Lead" RD and
construction activities. USACE may also provide
other technical assistance to EPA in support of
response actions.
1-3
EM 200-1-4
31 Jan 99
&
DSMOA/CA - DOD reimburses states and territories
up to one percent of the costs for technical services for
environmental restoration cleanups. USACE is
responsible for execution of activities which include
establishing, managing, implementing, and monitoring
the DSMOA/CA program.
&
Non-mission HTRW work for others - Through IAGs,
non-DOD Federal agencies utilize the technical
expertise and experience in work relating to the
RCRA, CERCLA, and underground storage tank
(UST) investigation and response actions under the
HTRW program for non-DOD Federal agencies.
&
Ordnance and Explosives (OE) CX is primarily
responsible for maintaining state-of-the-art technical
capabilities in OE, performing SIs, Engineering
Evaluations and Cost Analyses (EE/CAs), and
removal design phases of OE projects.
&
Divisions are responsible for providing program
oversight of all HTRW environmental restoration
projects and designating project management
assignments for HTRW projects.
&
HTRW design districts provide the Division
Commander with technical support in the areas of
health and safety, chemical and geotechnical data
quality management, environmental laws and
regulations, risk assessment, contracting and
procurement, and technical design and construction
oversight.
&
Geographic districts are responsible for managing the
execution of RAs as well as PAs, removal design, and
removal action related to the FUDS program.
Guidance for Civil Works projects - The Civil Works
districts may request technical support and guidance
from HTRW program elements.
1.2.4
HTRW Program Organization.
Army
Regulation (AR) 200-1 (USA) and USACE HTRW
Management Plan (USACE, 1996a) describe the USACE
organizational elements in support of DERP, BRAC, and
other programs. Their major responsibilities include, but
are not limited to, the following:
&
The Assistant Secretary of the Army for Installations,
Logistics, and the Environment (ASA [I,L,E]).
&
Headquarters, U.S. Army Corps of Engineers
(HQUSACE) - The Military Programs Directorate Environmental Restoration Division (CEMP-R)
develops, monitors, coordinates, and proposes
program management policies and guidance, and
provides funding and manpower requirements to the
program customers.
&
The Director of Environmental Programs (DEP)
within the office of the Assistant Chief of Staff for
Installation Management (ACSIM) is responsible for
interfacing with Department of the Army (DA)
components for policies and funds for
IRP/FUDS/BRAC executed by USACE.
&
HTRW Center of Expertise (CX) is primarily
responsible for maintaining state-of-the-art capability,
providing technical assistance to other USACE
elements, providing mandatory review of designated
HTRW documents, and as requested, providing
technical and management support to HQUSACE.
1-4
&
1.3 OVERVIEW OF HTRW RESPONSE PROCESS
HTRW response actions involve all phases of a site
investigation, design, remediation, and site closeout. The
HTRW response action process is phased and performed in
accordance with EPA procedures for assessing
uncontrolled hazardous waste sites under CERCLA or
RCRA. The following sections generally describe the
CERCLA and RCRA processes, which are functionally
equivalent to one another in objectives and types of site
decisions to be made throughout each process.
1.3.1
CERCLA Process. CERCLA, commonly known
as "Superfund," establishes a national program for
responding to uncontrolled releases of hazardous
substances into the environment.
The regulation
implementing CERCLA is the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP)
(USEPA, 1990c). In general, the CERCLA process
consists of the site assessment phase and the remedial
phase as described below; however, removal actions (as
allowed by the NCP) may be taken at any
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time during the CERCLA process. It should be noted that
the general framework established under the CERCLA
process has been adopted for use in environmental cleanup
under other programs, e.g., the cleanup of petroleum, oil,
and lubricants (POLs)1 at FUDS or active installations not
listed on the proposed or final National Priorities List
(NPL). Therefore, certain CERCLA project phases
described below (specifically, the Hazard Ranking System
[HRS], NPL, and site deletion), are not applicable to these
types of sites.
in such a way as to assure that adequate data is
available for EPA to perform the scoring.
&
DOD has developed the Relative Risk Site Evaluation
Primer (1994b) to rank sites primarily for resource
allocation and program management purposes.
Although neither a replacement nor alternative for
HRS scoring, this model suggests that stakeholders
consider evaluation factors (contaminant hazard factor,
migration pathway factor, and receptor factor) to
categorize sites according to "high," "medium," and
"low."2
&
NPL - Sites placed on the NPL (based on an HRS
score of 28.5 or greater, state nomination, issuance of
a health advisory by the Agency for Toxic Substances
and Disease Registry (ATSDR), or other method) are
published in the Federal Register and are eligible for
Superfund-financed RA. DOD sites on the NPL,
although not eligible for Superfund-financed RA, are
eligible for Defense Environmental Restoration
Account (DERA)-funded response actions.
1.3.1.1 Site Assessment Phase - To Identify Sites for
Further Evaluation.
&
Site Discovery - EPA identifies and lists in the
CERCLA Information System (CERCLIS) possible
hazardous substance releases to be evaluated under
Superfund.
&
PA - While limited in scope, a PA is performed on
sites listed in CERCLIS to distinguish sites which pose
little or no threat to humans and the environment and
sites that require further investigation or emergency
response.
&
&
SI - An SI identifies sites which (1) have a high
probability of qualifying for the NPL or pose an
immediate health or environmental threat that requires
a response action, (2) require further investigation to
determine the degree of response action required,
and/or (3) may be eliminated from further concern.
HRS - At the end of both the PA and SI, EPA applies
a scoring system known as the HRS to determine if a
site should receive a "no further remedial action
planned" recommendation or be listed on the NPL for
further action. An HRS can also be used to support
other site evaluation activities under CERCLA (see
The Revised Hazard Ranking System, USEPA,
1992a). Although HRS scoring is the EPA’s
responsibility, site investigations should be designed
1.3.1.2 Remedial Phase - To Determine the Degree of
Risk Based on Nature and Extent of Contamination and
Implement Cleanup Remedies if Warranted.
&
RI - The RI is a field investigation to characterize the
nature and extent of contamination at a site and
implement cleanup remedies if warranted. A BRA,
which includes both a HHRA and an ERA, is
performed as part of the RI. The BRA is a component
of the RI/FS report.
&
FS - Based on data collected during the RI3, remedial
alternatives are developed, screened, and analyzed in
detail. After potential alternatives are developed, they
are screened against three broad
2
1
POLs are not listed as hazardous substances under
CERCLA and therefore are not subject to CERCLA
response actions. However, unless the state has specific
requirements for remediating POL sites, the CERCLA
process may be utilized to address the site.
The Relative Risk Site Evaluation Primer (DOD 1994b)
has replaced the Defense Prioritization Model, which has
features comparable to the HRS.
3
If the BRA contained in the RI indicates that risks are
acceptable or insignificant, the FS will not be done and
the site will be closed out.
1-5
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31 Jan 99
criteria: effectiveness, implementability, and cost. Those
alternatives which pass this initial screen will be further
evaluated according to EPA’s nine criteria4 and other risk
management considerations not included in the criteria
(e.g., environmental justice under Executive Order (EO)
12898) before one or more of such remedies is proposed
for selection.5
&
Proposed Plan/Record of Decision (ROD) - After
the RI/FS process has been completed, a Proposed
Plan is made available for public comment. The
Proposed Plan identifies the remedies for the site
jointly selected by the lead agency and the support
agencies, and indicates the rationale for the selection.
All final decisions and response to public comments
are entered in a legal administrative record, the ROD.
&
RD/RA - RD is a subactivity in remedial
implementation where the selected remedy is clearly
defined and/or specified in accordance with
engineering criteria in a bid package, enabling
implementation of the remedy. RA is a subactivity in
remedial response involving actual implementation of
the selected remedy.
&
Five Year Review/Site Deletion - Upon completion
of all RAs, CERCLA and the NCP allow for the
reclassification or deletion of the site from the NPL. If
an RA results in any hazardous substances remaining
on site, CERCLA Section 121(c) requires a review of
the remedy once every 5 years to assure that: (1) the
site is maintained, i.e., the remedy (including any
engineering or institutional controls) remains
operational and functional; and (2) human
4
The nine criteria are: (1) overall protection of human
health and the environment; compliance with Applicable
or Relevant and Appropriate Requirements (ARARs); (3)
long-term effectiveness/permanence; (4) short-term
effectiveness; (5) reduction of toxicity, mobility, or volume;
(6) implementability; (7) cost; (8) state acceptance; and (9)
community acceptance.
5
If the RI shows no unacceptable risk, regulators may
agree to eliminate the FS and proceed directly to a noaction proposed plan.
1-6
health and the environment are protected, i.e., the cleanup
standards (based on risk or ARARs) are still protective.
1.3.1.3 Removal Action - To Prevent, Minimize,
Stabilize, or Mitigate Threat to Humans and the
Environment.
CERCLA Section 104 Removal Actions can take place at
anytime during the entire CERCLA process. Unlike RAs,
removal actions are not designed to comprehensively
address all threats at the site. Removal actions may be
emergencies (within hours of site discovery), time-critical
(initiated within 6 months), non-time-critical (planning for
the removal action takes 6 months or longer), or early
actions. EE/CAs, comparable to FSs, are required for
removal actions that are deemed non-time-critical.
1.3.2
RCRA Corrective Action Process. RCRA
requires corrective action for releases of hazardous waste
or hazardous waste constituents from Solid Waste
Management Units (SWMUs) at hazardous waste
Treatment, Storage and Disposal (TSD) Facilities with a
permit and those seeking a RCRA permit or approval of
final closure. The owner or operator of a facility seeking a
RCRA permit must:
&
Institute corrective action as necessary to protect
human health and the environment from all releases of
hazardous waste, and hazardous constituents from any
SWMU at the facility.
&
Comply with schedules of compliance for such
corrective action.
&
Implement corrective actions beyond the facility
boundary.
The corrective action process has four main components:
an RFA, an RFI, a CMS, and a CMI.
&
RFA - An RFA is designed to identify SWMUs which
are, or are suspected to be, the source of a release to
the environment. The RFA begins with a preliminary
review of existing information on the facility, which
may be followed by a visual site inspection. The RFA
will result in one or more of these actions: (1) NFA is
required, (2) an RFI is to
EM 200-1-4
31 Jan 99
be conducted to further investigate the documented or
suspected releases, (3) interim measures are necessary to
protect human health or the environment, and (4) referral
to other authorities to address problems related to permitted
releases.
&
&
RFI - An RFI may be required based on the outcome
of the RFA. An RFI is accomplished through either a
permit schedule of compliance or an enforcement
order. The extent of the investigation can vary widely
since the investigation site may encompass a specific
SWMU or a larger area of concern (AOC) that
includes several SWMUs. The RFI results will effect
one or more of these actions: (1) NFA is required, (2)
CMS is necessary, (3) interim corrective measures are
necessary, or (4) referral to another authority to
address problems related to permitted releases.
CMS - A CMS is an "engineering evaluation"
designed to evaluate and recommend the optimal
corrective measure(s) at each SWMU where
contaminant levels exhibit unacceptable risks.
Medium-specific cleanup levels protective of human
health and ecological receptors are developed, and the
boundaries or point(s) of compliance are set. At this
project phase or before the CMI phase, RCRA
provides the designation of an AOC in which
remediation wastes may be moved and managed
(according to the approved corrective measures)
without triggering land disposal restriction regulations
under 40 CFR Part 268. Note that a typical CMS is
more focused than is usually done for CERCLA FSs.
The remedy selected from all potential remedial
alternatives, including the "NFA" alternative, should
be based on four criteria:
-
Protection of human health and the environment.
-
Attainment of media cleanup standards.
-
Control of sources to eliminate harmful releases.
-
Compliance with RCRA's waste management and
disposal requirements.
&
CMI - A CMI includes the actual design, construction,
operation, maintenance, and periodic evaluation of the
selected corrective measures.
EPA can impose interim corrective measures on RCRA
facilities under corrective action to protect human health
and the environment. The interim corrective measures can
be taken at any time during the corrective action process.
EPA is accelerating cleanups at RCRA corrective action
sites by promoting the reduction of exposure and further
releases of hazardous constituents until long-term remedies
can be selected. These accelerated cleanup actions are
known as "Stabilization Initiatives" (USEPA, 1992n) and
are similar in concept and application to the Superfund
Accelerated Cleanup Model (SACM) under CERCLA
(USEPA, 1992g).
1.3.3
Functional Equivalency of the CERCLA and
RCRA Processes. The RCRA and CERCLA programs
use different terminology, but follow parallel procedures in
responding to releases. In both programs, the first step
after discovery of a site is an examination of available data
to identify releases needing further investigation. This step
is called PA/SI in the CERCLA process and RFA in the
RCRA process. If imminent human health and/or
environmental threats exist, a mitigating action is
authorized, known as a removal action under CERCLA
Section 106 or an interim measure under RCRA Section
7003 or 3005(c)(3). Both programs require an in-depth
characterization of the nature, extent, and rate of
contaminant releases, called an RI in the CERCLA process
and an RFI in the RCRA process. This is followed by a
formal evaluation and selection of potential remedies in the
FS (CERCLA) or CMS (RCRA) project phase. The
selected remedy is executed by a RD/RA under the
CERCLA process or CMI under the RCRA process. A
specific discussion of the functional equivalency of both
programs is presented in the preamble discussion of the
July 27, 1990 proposed rules for Corrective Action for
SWMUs at Hazardous Waste Management Facilities. A
diagram comparing the RCRA and CERCLA processes is
presented in Figure 1-1.
1.3.4
Role of Risk Assessment in the HTRW
Process. Risk assessment has been consistently used as a
decision-making tool in one or more steps in the
1-7
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31 Jan 99
RCRA PROCESS
CERCLA PROCESS
RCRA FACILITY ASSESSMENT (RFA)
&
&
&
PRELIMINARY ASSESSMENT (PA)
&
LIMITED SAMPLING
VISUAL SITE INSPECTION
REVIEW OF SITE RECORDS
REVIEW SITE RECORDS TO DETERMINE IF
FURTHER ACTION IS NEEDED
SITE INSPECTION (SI)
&
GATHER BASIC INFORMATION (LIMITED
FIELD INVESTIGATION)
HAZARD RANKING SYSTEM (HRS)
SCORES > 28.5
&
DETERMINE IF AN RFI, INTERIM
CORRECTIVE MEASURE, OR NO FURTHER
ACTION IS APPROPRIATE
&
DETERMINE IF SITE IS PLACED ON NPL OR
REMOVAL ACTION SHOULD BE TAKEN OR
“NO FURTHER ACTION DECISION”
NATIONAL PRIORITY LIST (NPL)
RCRA FACILITY INVESTIGATION (RFI)
&
&
REMEDIAL INVESTIGATION (RI)
CAN RANGE FROM SMALL, SPECIFIC
ACTIVITIES TO COMPLEX, MULTIMEDIA
STUDIES
FIELD SAMPLING
&
CORRECTIVE MEASURES STUDY (CMS)
&
IDENTIFY AND RECOMMEND SPECIFIC
MEASURES TO CORRECT RELEASES
AND POSSIBLE REMEDIAL ACTIONS
DETERMINE NATURE AND EXTENT OF
CONTAMINATION
FEASIBILITY STUDY (FS)
&
EVALUATION OF ALTERNATIVES TO
SELECT THE PREFERRED CLEANUP OPTION
* INTERAGENCY AGREEMENT (IAG)
STATEMENT OF BASIS
RECORD OF DECISION (ROD)
CORRECTIVE MEASURES
IMPLEMENTATION (CMI)
REMEDIAL DESIGN (RD)
REMEDIAL ACTION (RA)
* Note that the IAG is required by statute to follow
completion of the FS. However, it is DOD policy to initiate
the IAG following placement on the NPL.
1-8
LONG-TERM MONITORING
and/or
NPL DELETION
Figure 1-1. Comparison of RCRA and CERCLA processes.
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31 Jan 99
CERCLA and RCRA corrective action processes. A risk
screening analysis is used during the PA/SI to determine
whether a site may be eliminated from further concern or
requires further study, which may be focused on specific
areas of the site. A BRA is conducted in the RI. Section
105 of CERCLA/SARA charges the On-Scene
Coordinator or Remedial Project Manager (RPM) with the
responsibilities of identifying potential impacts on public
health, welfare, and the environment, and setting priorities
for this protection which is delegated to DOD under
Section 115 and EO 12580 for DOD facilities. RCRA
Section 3019 requires the facility owner/operator to
submit an Exposure Information Report (EIR) which
provides exposure and health assessment information for
certain storage and land disposal waste management units.
In the RFI, as required by permit conditions or
enforcement actions under RCRA Sections 3008(h), 7003,
and/or 3013, a Health and Environmental Assessment
(HEA) is used to determine quantitatively if the site or any
of its units has exceeded established health criteria. As
indicated in the RFI guidance (USEPA, 1989f), a sitespecific risk assessment will be performed prior to the
CMS to assess potential risk to humans and to determine
if no response action is appropriate. Under CERCLA
Section 120, the BRA is one of the primary documents
identified for submission to EPA for comment and review
in the Federal Facility Agreement (FFA).
Risk assessment in reverse is used to develop risk-based
Remediation Goals (RGs) under CERCLA or Target
Cleanup Levels (TCLs) (CERCLA Section 121) or
Alternate Concentration Limits (ACLs)6 under RCRA (40
CFR 264.94 and 264.100). Risk-based RGs, TCLs, or
ACLs should be developed after the BRA has been
performed incorporating site-specific factors in the
calculations. Preliminary Remediation Goals (PRGs),
corrective action levels, or soil screening levels can be
developed at any time in the site investigation process, to
determine whether further action is appropriate and to help
focus subsequent studies on significant pathways of
exposure. The summary or conclusions of the RI BRA,
development of RGs based on allowable exposure, and
analysis of alternatives (based on risk and the other criteria)
are part of the FS report (USEPA, 1988i).
To be protective of human health, interim corrective
measures or remedial alternatives must also be evaluated
based on their ability to reduce site risk and their potential
impact to humans during and after remediation. This risk
evaluation of remedial alternatives is part of the remedy or
corrective measure selection process prior to RD/RA
(CERCLA Section 121, NCP Section 300.430(e)(1)), and
Proposed RCRA Corrective Action Rule, Section 264.525(b)(55 FR 30798, July 27, 1990 and 61 FR
19431, May 1, 1996).
Performing a risk assessment is an iterative process. Risk
assessment information is continuously being collected
during the HTRW site investigation process, leading to the
characterization of risks and uncertainties qualitatively or
quantitatively. Risk assessment information is used during
various stages of the HTRW site decision process as
described below:
1.3.4.1 PA/SI, RFA, or Other Preliminary Site
Investigation Activities. In this phase of the site
investigation process, risk assessment information is used
to determine whether a site may be eliminated from further
concern, to identify emergency situations which may require
immediate response actions/interim corrective measures, to
assess whether further site
investigations are required, to develop a data collection
strategy, and to set site priority (e.g., to rank sites).
It is important that the limited information gathered in this
phase support the risk screening analysis and the HRS
scoring if further site investigations are required. Accurate
site information should be made available to the ATSDR in
an attempt to avoid having health consultations or an
advisory issued for the site by ATSDR based on inaccurate
site information.7
7
6
ACLs are allowable for ground water contamination
only and do not address contamination of other media.
Cleanup levels for surface water, sediment and soil are
determined utilizing risk assessment as is done in
CERCLA.
Under CERCLA Section 104(j)(6), ATSDR is required
to conduct health assessment under this Section for sites
where individuals may have been exposed to a hazardous
substance for which the source is related to a CERCLA
release. Health assessments are generally based on SI, RI,
Superfund risk assessment (human health evaluation), and
studies submitted to ATSDR. In addition, ATSDR may
conduct an analytical investigation that evaluates the
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1.3.4.2 RI, RFI, or Other Additional Site Investigation
Activities. In this phase of the site investigation process,
existing chemical data and other exposure information are
generally available. Data collected in this phase should
comprise those media and pathways identified in the
preliminary screening, including background data. If the
data are useable and appropriate for the potential exposure
pathways considered to be complete, baseline risks can be
estimated. The results of the risk assessment will be used
in the FS to determine the degree of response action
required. RAs should be initiated to address the risks
associated with an operable unit (OU), a SWMU, an area
of contamination (AOC), an area of interest/concern, or an
exposure area or unit.
An OU, as defined in the NCP, “is a discrete action that
comprises an incremental step toward comprehensively
addressing site problems.” OUs provide a procedural
basis for phasing multiple control measures that make up
an RA, which may be used as a construction management
tool during installation of complex RA, and which can
provide manageable geographic areas for study. Areas of
a site which are concerned with a specific receptor group
may be used as the basis of OU designation which allows
for effective evaluation of exposure pathways, simplifying
the risk assessment of the site into manageable
components. DOD facilities are much larger than
traditional Superfund sites, and designation of OUs is an
important part of designing the risk assessment to
effectively define RA requirements.
To avoid triggering RCRA land disposal restrictions or
minimum technology requirements, OUs may be combined
to form an AOC for the purpose of implementing response
action. A similar concept has been applied for combining
SWMUs. It should be noted that the BRA completed in
the RI serves to identify the need for response action and
the relative degree of response required based on
protection of human health and the environment.
1.3.4.3 FS, RD/RA, CMS/CMI, or Other RD and
Implementation Activities. During the feasibility, treatability, or other remedial measure study phase, an evaluation of
short-term and long-term risks associated with remedial
alternatives is required under CERCLA Section 121, as is
the development of cleanup levels.
Risk-based RGs/TCLs/ACLs can be derived based on
EPA-established procedures (e.g., RAGS Parts A and B).8
Specifically, risk assessment will be used to select a remedy
by comparing among the alternatives the potential
human/environmental impact during remediation (shortterm and long-term) and the residual risks after remediation.
This comparative analysis can be performed qualitatively
for the ability of the alternatives to achieve the RGs, TCLs,
ACLs (along with other criteria such as cost and long-term
effectiveness). A more effective approach for many sites
will be to perform quantitative evaluation of the risks
associated with each remedial alternative or corrective
measure, based on the alternative's long-term and shortterm impact on risk to receptors. All potential receptors
during and after the RA periods should be considered.
As with environmental monitoring, risk assessment can play
a key role in assessing the residual risks and to establish
ACLs. It can be used as a measuring tool to gauge the
success of the RAs or corrective measures. See RAGS,
Part C (USEPA, 1991e), Alternate Concentration Limit
Guidance Part 1 - ACL Policy and Information
Requirements (EPA 1987b), and Alternate Concentration
Limit Guidance Based on 264.94(b) Criteria, Case Studies
(EPA 1988f).
1.3.4.4 Use of Risk Assessment in Special Studies. Risk
assessment techniques are used in virtually all phases of
CERCLA, RCRA, and other HTRW processes. Therefore,
risk assessment should be planned for and conducted to provide input to discussions associated with each phase. There
are also special studies in addition to
8
possible causal relationships between exposure to
hazardous substances and disease outcome by testing a
scientific hypothesis. Exchanges of information and
reports with ATSDR will be coordinated through the U.S.
Army Center for Health Promotion and Preventive
Medicine (USACHPPM).
1-10
This manual emphasizes the need for careful HTRW
project planning for adequate data collection to support a
site decision. Risk assessment is a powerful decision
tool; yet, misapplication of risk assessment procedures
and concepts and poor data quality and quantity could
lead to inaccurate assessment of risk and may lead to
incorrect or poor site decisions.
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executable phases discussed previously, specifically,
protectiveness or “How clean is clean?” The following are
examples of risk assessment in special studies:
&
&
&
9
ARAR waiver - EPA has indicated that a non-zero
Maximum Contaminant Level Goal (MCLG) is an ARAR in the remedy selection. MCLG does not take
into account specific site conditions and exposure
patterns or economic and technical feasibility of
implementation. Even though the non-zero MCLG
may be considered an ARAR, a risk assessment can
be used to evaluate the appropriateness of the nonzero MCLG. If a site-specific alternative cleanup
level is as protective, an ARAR waiver request may
be submitted under CERCLA Section 121(d)(2). The
same process may be used to waive state ARARs,
some of which are based on aesthetics including sight
and odor.9
Emergency response - The effectiveness of a
proposed removal action, particularly for nontime-critical response action, should be evaluated in
terms of the ability of the response action to reduce
exposure. A screening risk assessment can be
conducted to evaluate the response actions for
relatively straightforward sites, although a BRA may
be more appropriate for complex sites and cost recovery actions. This is particularly critical since EPA
and some states want to implement early actions and
presumptive remedies for certain sites. USACE
HTRW risk assessment staff and design districts
should consider all options, based on effectiveness of
the action, and other criteria in the risk reduction
efforts.
Compliance with state air programs - CERCLA and
RCRA sites are potential sources of air emissions.
These air emissions may be present before and/or
during the response action (removal or remediation),
or during the operation and
EPA has compiled thresholds for odor for chemicals
based on an extensive literature search. The updated
odor thresholds should be consulted to evaluate if the
ARAR (if based on odor) is reasonable. See Reference
Guide to Odor Thresholds for Hazardous Air Pollutants
Listed in the Clean Air Act Amendments of 1990,
(USEPA, 1992f).
maintenance of the response action. Of particular concern
are volatile and semivolatile organic chemicals, particulate
matter, heavy metals, and acids. Operations implemented
during the cleanup process (i.e., RI, removal action, or
construction of a selected remedy) may emit air pollutants.
Examples of operations which may act as a source of air
emissions include soil handling, air stripping, onsite
incineration,
and
equipment
used
in
solidification/stabilization processes.
USACE risk
assessors should consult with state air regulatory personnel
to determine the exact risk assessment requirements for
evaluating air pathway exposures within that state. If
potential risks are determined following state guidelines,
resulting requirements for air emission limitations or
emission control technologies should be discussed with the
appropriate USACE personnel on the RD team.
&
Risk assessment will be useful to assess the impact of
the response actions (new sources) and the baseline
condition (an existing source), for attainment of the
National Ambient Air Quality Standards and
substantive requirements embodied in the State
Implementation Plan (SIP). See ARAR Fact Sheet Compliance with the Clean Air Act and Associated Air
Quality Requirements (USEPA, 1992l).
1.4 CONCEPT OF RISK ASSESSMENT AND GOOD
SCIENCE
Risk assessment can be qualitative or quantitative. It
includes an integration of hazard (dose and response),
exposure (intake), and characterization of the potential
risks/hazards and uncertainties. The process relies on
strong fundamental scientific principles; the management
aspect relies on application of policy as well as
professional judgment and experience. This view is
reflected by the National Academy of Sciences (NAS) and
EPA who recognized the inherent uncertainties in the risk
assessment methodologies. The uncertainties are primarily
caused by various unknowns in the risk estimate calculation,
which, in many cases, requires making assumptions relating
to predictive modeling or inferences of certain scientific
principles (Federal Focus
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Inc., 1991).10 This paragraph highlights the principles,
instructions, or recommendations of assessing the impact
on human health from chemicals in the environmental
media at HTRW sites.
1.4.1
Basic Concepts. The fundamental principles of
good science and quality entail the thorough understanding
of: (a) site chemical data; (b) an understanding of siterelated and background risks; (c) physical, chemical, and
toxicity information associated with site chemicals; (d) fate
and transport of site chemicals; (e) intake and extent of
absorption; (f) the dose-response relationship of site
chemicals; (g) uncertainties and limitations of the derived
risk estimate;
10
There can be significant uncertainties in the input
parameters used in the risk assessment model, assuming
that the model is the best scientific representation which
can be used to predict potential health consequences from
the exposure to chemicals in the environment. Since these
models are used to support site decisions and policymaking, quantitative examination of these uncertainties is
important. Presentation of risk estimates under the
average and reasonable maximum exposures (RME) is
now required by EPA's Superfund office. Recently, there
has been an increased use of Monte Carlo (MC) analysis
to propagate uncertainties through repetitive risk
assessment calculations. Two examples of the application
of MC are: (1) to determine a more accurate estimate of
“reasonable maximum” risk than the use of standard
default (normally high end) values for exposure input
factors which could magnify risks to the Theoretical Upper
Bound Estimate region of the risk probability curve, and
(2) to evaluate the trade-off between extent (and thus cost)
of remediation and degree of confidence in achieving
adequate protection of health. MC can be used to provide
risk estimates based on simulations of only a few key
parameters which could substantially impact risks. These
parameters are normally identified by performing a
sensitivity analysis which compares the relative impact on
the risk estimates (ranges) associated with each input
parameter's maximum and minimum values while keeping
other parameter values unchanged. There are off-the-shelf
computer software programs for MC analysis in risk
assessment, e.g., Crystal Ball®, At-Risk®, and others.
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and (h) the best approach to characterize risk objectively.
The application of good science or definition of quality in
the risk assessment reduces or defines uncertainties in a risk
assessment. This application results in an unbiased risk
characterization which allows risk managers to make
informed site decisions. If the risk assessment uncertainties
are well documented, and the results presented in a manner
which can be easily understood by decision-makers, then
this element of decision-making has more meaning relative
to the other elements of risk management.
1.4.2
Risk Assessment as Decision Criteria in the
HTRW Program. The role of a risk assessment in the site
decision-making process at CERCLA and RCRA
Corrective Action sites has been well defined by EPA either
through rule-making or program directive/guidance.
Therefore, risk assessments have been used as decision
criteria in the USACE's HTRW program involving
CERCLA and RCRA sites. For BRAC, FUDS, or other
HTRW work which may not be on the NPL, risk
assessments should be similarly applied. Activities at these
sites require the evaluation of potential health and
environmental risks in order to return the property to
conditions appropriate for the current and planned future
land uses. Therefore, a site-specific BRA is an important
decision tool to USACE customers. If cleanup is needed,
the extent or level of cleanup required will be based on
results of the BRA, in addition to ARARs or other non-risk
factors. Therefore, risk assessment is used as a decision
tool at all HTRW response action sites.
1.5 POLICY CONSIDERATIONS
MANAGEMENT
AND
RISK
This section presents a general discussion of the influence
of policy considerations in risk assessment and risk
management. Because of the implications of policy
considerations on the site decision process, the risk
assessors and risk managers are encouraged to identify the
policies early in the decision process.
Unlike regulations which are enforceable, policies or
published guidelines are administrative procedures or
requirements concerning certain environmental regulations.
DOD has issued directives to components (Army, Navy, Air
Force, and Defense Logistic Agency),
EM 200-1-4
31 Jan 99
reaffirming DOD's commitment to comply with specific
environmental laws or EOs. The respective components
have also issued directives or orders expressing the same
procedures or requirements. USACE will follow such
policies or directives issued by DOD or its components
regarding compliance with Federal environmental laws in
the execution of HTRW response action at DOD
installations or facilities. Some states or regional
environmental control boards have also issued
environmental policies or guidance. In the unlikely event
that a policy is scientifically incongruent with site
situations, early identification and resolution are critical.
HQUSACE or HTRW CX technical staff should be
consulted in these instances. All major policies used in
making site decisions should be identified in the ROD or
site decision documents so that the USACE customers and
other stakeholders can judge the merit of these policies in
achieving protection of human health and the environment.
1.5.1
Relationship Between Policy Considerations
and Risk. A risk assessment is the technical evaluation of
the degree of hazard or risk associated with exposure to
contamination of an environmental medium or media.
Risk management is oriented toward deciding whether
RAs are warranted in light of the results of a risk
assessment. The NAS National Research Council (NRC)
defines risk management as "the process of weighing
policy alternatives and selecting the most appropriate
regulatory action, integrating the results of risk assessment
with engineering data and with social, economic and
political concerns to reach a decision" (NRC, 1983). NAS
has identified four key components in managing risk and
resources: public participation, risk assessment, risk
management, and public policy decision-makers (NRC,
1994).
In making risk management decisions, the risk manager
considers the degree of risk, technical feasibility to address
risk, costs and benefits, community acceptability,
permanence of the proposed actions, and other similar
factors which are subject to policy considerations or
regulatory requirements. As such, risk management is an
important part of the USACE HTRW site response
process, as it combines results of the risk assessment,
regulatory requirements, and applicable agency policies
(e.g., applicable DOD policies for defense sites).
1.5.2
USACE Policy Considerations. In an effort to
standardize risk assessment procedures within the USACE
HTRW program, the following considerations should be
consistently applied to all site-specific risk assessments.
Although not designated as DA or USACE policy at this
time, these issues are based on sound science and will assist
in making risk management decisions. At the appropriate
locations within the text (see paragraph references below),
these policy considerations are presented in bold typeface
within double outlined text boxes, including implementation
directives, as required.
&
The risk assessment shall be given, at a minimum,
equal consideration with other factors in the risk
management decision. See Paragraph 6.1.
&
All risk assessments shall include a statistically robust,
significant, and defensible set of background
concentrations. See Paragraph 4.3.3.2.2.
&
Future land uses for risk assessment purposes and for
development of remedial action objectives (RAOs)
shall be land uses that are reasonably expected to occur
at the site or facility. See Paragraph 4.4.4.
&
If the cumulative site risk calculated in the risk
assessment does not exceed 1E-04 for reasonable
exposure scenarios, ARARs are not exceeded, and
ecological impacts are not significant, no RA should be
required. See Paragraph 6.2.2.
&
The exposure assessment of a risk assessment shall
utilize site-specific frequencies and durations whenever
possible. A minimum of two risk estimates should be
presented for each land use scenario, the RME and the
central tendency (CT). See Paragraphs 4.4.5.1.3 and
4.4.5.1.6.
&
Use of the EPA’s Integrated Exposure Uptake and
Biokinetic (IEUBK) model for lead exposures should
be limited to residential, childhood exposures only.
Where non-residential exposures are expected, an adult
lead intake model should be used. See Paragraph
4.5.7.1.2.
&
RGs must be developed and applied in the context of
exposure area and exposure point concentrations. It
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is unnecessary to remediate all media to or below the RG.
See Paragraph 5.2
HTRW risk assessors to clearly identify these instances as
potential uncertainties as well.
1.5.3
EPA Headquarters, Regional and State
Policies. To successfully complete a risk assessment for
use in making site decisions, HTRW project managers
(PMs) and risk assessors generally work with Federal,
regional, and state regulatory agencies to identify their
specific policies or procedural requirements. HTRW risk
assessors should identify and assist, where appropriate, in
negotiations with the agencies on policies, procedures, and
assumptions which are questionable.
1.6 REGULATORY DIRECTIVES AND GUIDANCE
All HTRW response actions should be in compliance with
the Regulatory Policy Guideline issued under EO 12498
(1985), which states, "Regulations that seek to reduce
health or safety risks should be based upon scientific risk
assessment procedures, and should address risks that are
real and significant rather than hypothetical or remote."
Whenever possible, USACE's HTRW position should be
supported by scientific principles, site data, or literature
values. USACE recognizes that at times, agencies have to
set policies in the absence of scientific consensus;
however, USACE, through the HTRW program, is
responsible for applying such policies properly and
objectively based on site-specific considerations.
1.5.4
Risk-Based Management Decisions for Site
Actions. Risk managers select the most appropriate
remedy by considering "trade-offs" among different
remedial alternatives and evaluating the ability of the
alternatives to accomplish the overall project objectives.
To improve the quality of risk-based management site
decisions, HTRW risk assessors should identify key
information that can affect that decision-making. This
information should include policy considerations,
assumptions concerning the margins of safety, and the use
of other relevant data not associated with the site in the
risk assessment. The sources of such policies and data, as
well as the qualifications of persons/organizations
recommending the policies or use of data, should be
clearly identified. HTRW risk assessors can further help
risk managers by providing an explanation of uncertainties
in the risk assessment. When science deviates from
policies or assumptions inherent in the risk assessment, it
is the responsibility of
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This section highlights major EOs, Federal
statutes/regulations under which the HTRW programs
operate, and EPA risk assessment guidelines which provide
the basis for development of this handbook. Irrespective of
the procedures or mechanics for conducting risk
assessments according to regulatory guidelines, all risk
assessments performed under the HTRW response action
must be based on "good science" and reasonable and
unbiased scientific judgment. Although this section lists
only major applicable EOs and directives, others may be
accessed through the appropriate agencies and databases on
the Internet.
1.6.1
EOs and Federal Statutes/Regulations.
EO 12088 (1978), Federal Compliance with Pollution
Control Standards, established the mechanism by which
the Executive Branch assures that its facilities (in various
departments) meet their compliance responsibilities by
complying with substantive and procedural requirements of
Federal environmental statutes. These statutes include:
Endangered Species Act (ESA); the Clean Air Act (CAA);
the Federal Water Pollution Control Act (Clean Water Act
[CWA]); the Solid Waste Disposal Act (as amended by
RCRA); the Noise Control Act; the Marine Protection,
Research and Sanctuaries Act (Ocean Dumping Act); the
Safe Drinking Water Act (SDWA); the Toxic Substances
Control Act; the Federal Insecticide, Fungicide, and
Rodenticide Act; and the National Historic Preservation
Act.
EO 12498 (1985), Government Management, incorporates
by reference the regulatory principles contained in a Task
Force report regarding future significant regulatory actions.
Two principles of interest are:
&
Regulations that seek to reduce health or safety risks
should be based upon scientific risk-assessment
procedures, and should address risks that are real and
significant, rather than hypothetical or remote; and
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31 Jan 99
&
To be useful in determining overall benefits and costs,
risk assessments must be scientifically objective and
include all relevant information. In particular, risk
assessment must be unbiased best estimates, not
hypothetical "worst cases" or "best cases." In
addition, the distribution of probabilities for various
possible results should be presented separately, so as
to allow for an explicit "margin of safety" in final
decisions.
EO 12580 (1987), Superfund Implementation, requires
all Federal agencies to comply with CERCLA/SARA and
NCP in the same manner as the private sector. This Order
delegated to the Secretary of Defense the response
authority of DOD, which includes removal/RAs, site
investigation and risk assessment, remedy selection,
performance of PAs, and assuming natural resource
trustee's responsibilities for current and former DOD
facilities, and others. The Office of the Deputy Under
Secretary of Defense for Environment Security
(ODUSD[ES]) is responsible for carrying out the
Secretary's responsibilities and administering the DERP in
compliance with this Order.
EO 12777 (1991), Implementation of Section 311 of the
Federal Water Pollution Control Act of October 18, 1972
and the Oil Pollution Act of 1990, delegates to the EPA
and Coast Guard various responsibilities assigned to the
President under CWA Section 311 and the Oil Pollution
Act of 1990.
Other relevant EOs include: EO 11990 (1977), Protection
of Wetlands and EO 11988 (1977), Floodplain
Management.
RCRA 1976, as amended by the HSWA of 1984, has the
objectives to protect human health and the environment,
reduce waste and conserve energy/natural resources, and
to reduce or eliminate generation of hazardous waste:
&
Subtitle D - solid waste (encourages states to develop
and implement solid waste management plans to
provide capacity).
&
Subtitle C - hazardous waste program (identifies
hazardous wastes and regulates their generation,
transportation, and TSD; authorizes states to
implement the hazardous waste program in lieu of
EPA; requires permits for TSD facilities).
&
Subpart S - Proposed Corrective Action Rule
(provides procedures for implementing RCRA
corrective action) (55 FR 30797, July 27, 1990 and 61
FR 19431, May 1, 1996).
&
Subtitle I - UST (regulates petroleum products and
hazardous substances stored in underground tanks;
requires compliance with performance standards for
new tanks; and requires leak detection, prevention,
closure, financial responsibility, and corrective action).
CERCLA of 1980, as amended by the SARA of 1986 (42
U.S.C. 9601 et seq.) provides broad Federal authority to
respond directly to releases or threatened releases of
hazardous substances that may endanger public health or
the environment. SARA defines the process Federal
agencies must follow in undertaking RA, including a
requirement that EPA make the final selection of remedy if
there is a disagreement between the Federal agency and
EPA.
The NCP (55 FR 8660, 9 March 1990) provides
procedures and standards for how EPA, other Federal
agencies, states, and private parties respond under
CERCLA to releases of hazardous substances. The NCP
authorizes the U.S. Department of Interior and other
agencies, states, or entities to be the "trustees" of natural
resources to recover compensatory damages for "injury to,
destruction of, or loss of natural resources resulting from a
discharge of oil into navigable waters or a release of a
hazardous substance."
Federal Facility Compliance Act (PL-102386, October 21,
1992) directs Federal agencies to comply with Federal and
state environmental laws, and provides authority to EPA to
impose penalties on other Federal agencies for
noncompliance. Among others, it amended Section 6001 of
RCRA to waive immunity of the United States (Federal
department, agency, or instrumentality of the United States)
to administrative orders and civil penalties or fines
associated with Federal, state, interstate, and local solid and
hazardous waste management requirements. Section 3004
of RCRA was also amended to require EPA, in consultation
with DOD, to identify and regulate waste military munitions
which are hazardous.
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1.6.2
score, including identification of sites for emergency
response actions.
DOD Directives.
DOD Directive 5100.50 (DOD, 1973), Protection and
Enhancement of Environmental Quality, establishes
procedures and assigns responsibilities for use of DOD
resources in the protection and enhancement of
environmental quality and establishes the DOD Committee
on Environmental Quality.
&
Guidance for Performing Site Inspections Under
CERCLA (USEPA, 1992m). This document provides
the approaches, data acquisition planning needs,
sampling strategies, data evaluations using the SI
worksheets, and reporting requirements for the
CERCLA SI. The document describes the approach of
using a focused SI to test the PA hypotheses, resulting
in one of three recommendations: (1) site evaluation
accomplished, (2) expanded SI to collect additional
data, or (3) preparation of an HRS package for
placement of the site on the NPL if the HRS scoring
data requirements have been met.
&
Hazard Ranking System Guidance (USEPA, 1992a)
provides guidance to individuals responsible for
preparing HRS packages for sites for of sites on the
NPL.
&
Guidance for Conducting Remedial Investigations
and Feasibility Studies Under CERCLA (USEPA,
1988i). This guidance describes the CERCLA RI/FS
process to characterize the nature and extent of
contamination or risks posed by a site and to evaluate
whether RA is needed. It describes the site
characterization techniques, the role of a BRA,
feasibility studies, and development of screening and
detailed analyses of remedial alternatives.
&
Guidance for Data Useability in Risk Assessment
(Part A) (USEPA, 1992h) and (Part B) (USEPA,
1992k).
These guidance documents provide
approaches and recommendations for defining,
planning, and assessing analytical data for the BRA.
RAGS was published in two volumes: Volume I,
Human Health Evaluation Manual (USEPA, 1989j),
and Volume II, Environmental Evaluation Manual
(USEPA, 1989b). A compendium method handbook
(USEPA, 1989c) was published concurrently with the
Environmental Evaluation Manual. As the science of
ecological risk assessment has developed, additional
guidance has been published to superceed the
Environmental Evaluation Manual. Ecological Risk
Assessment Guidance for Superfund: Process for
Designing and Conducting Ecological Risk
Assessments was published as Interim Final on June
DOD Directive 5030.41 (DOD, 1977a), Oil and
Hazardous Substances Pollution Prevention and
Contingency Program, sets forth DOD policy in support
of the NCP.
DOD Directive 4120.14 (DOD, 1977b), Environmental
Pollution, Prevention, Control, and Abatement,
implements within DOD new policies provided by EO
12088 and Office of Management and Budget (OMB)
Circular A-106, and establishes policies for developing
and submitting plans for improvements needed to abate air
and water pollution emanating from DOD facilities.
DOD Directive 6230.1 (DOD, 1978), Safe Drinking
Water, sets forth DOD policy for provision of safe
drinking water and compliance with the SDWA.
DOD Directive 6050.1 (DOD, 1979), Environmental
Effects in the United States of DOD Actions, implements
the Council of Environmental Quality (CEQ) regulations
and provides policies and procedures to take into account
environmental considerations in DOD actions.
1.6.3
EPA Headquarters and Regional Guidance.
CERCLA
Guidance documents (Office of Solid Waste and
Emergency Response [OSWER] Directives) for
conducting various phases of a CERCLA response action
have been developed or are being finalized by EPA
headquarters. Key CERCLA guidance documents are
identified below (also see Appendix A):
&
Guidance for Performing Preliminary Assessments
Under CERCLA (USEPA, 1991c). This document
provides the PA objectives, data requirements, the
procedural steps to complete the PA, and develops a
site score using PA score sheets. It also provides
guidelines for reviewing the site evaluation and
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&
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approaches for lead risks, radionuclide risks,
probabilistic analyses, and ecological evaluation
that will be issued as revisions to RAGS Part D.
5, 1997 (USEPA, 1997b) and the Guidelines for
Ecological Risk Assessment, published as Final in April
1998 (USEPA, 1998b). Volume I has four parts:
-
Part A (USEPA, 1989j) provides a detailed
discussion on how a BRA should be conducted.
It presents key components of a risk assessment:
data collection and evaluation,
exposure
assessment,
toxicity
assessment,
risk
characterization, and uncertainty discussion.
-
Part B (USEPA, 1991d) presents the
methodologies and algorithms to calculate riskbased PRGs for individual chemicals in the soil,
ground water, and air media, and the
transformation of PRGs to RGs or cleanup levels
using site-specific information. It stresses that
risk-based cleanup levels are to be considered
along with ARARs, remediation technology, and
analytical detection limits (DLs), etc., in the risk
management and remedy selection processes.
-
-
Part C (USEPA, 1991e) presents the approach
and risk information used to evaluate remedial
alternatives during the FS. The evaluation
(either qualitative or quantitative) compares riskbased benefits of alternatives, investigates
potential risks to the nearby communities (shortterm and long-term/residual) and remediation
workers (short-term), determines the need for
engineering controls to mitigate potential risks,
and assesses the need for a 5-year review
indicated in the NCP. The guidance describes
selected remediation technologies and provides
references for quantifying the potential releases
from conducting such remedial activities.
Part D (USEPA, 1998a). The EPA was directed
to establish national criteria to plan, report, and
review Superfund risk assessments. The RAGS
Part D approach includes three basic elements:
(1) Use of the Standard Tools, (2) Continuous
Involvement of EPA Risk Assessor, and (3)
Electronic Data transfer to the National
Superfund Database. Additionally, EPA is
developing standard
The approach contained in RAGS Part D is
intended for all CERCLA risk assessments. Its
use is also encouraged in ongoing risk
assessments to the extent it can efficiently be
incorporated into the risk assessment process.
Part D is also recommended for non-NPL sites,
BRAC sites and RCRA sites when appropriate.
Chapter 1 of RAGS Part D provides more detailed
guidelines regarding its applicability as a function
of site lead and site type. Each EPA region will
determine the site-specific applicability, but
USACE risk assessors should consider its use on
all projects.
&
EPA regional guidance documents for risk assessment.
Various EPA regions have also supplemented the
national EPA risk assessment guidance with their own
policies and procedures for use in conducting a BRA.
These guidance documents, in the form of memoranda,
directives, or stand-alone documents, address a wide
range of issues. These issues include adjustment of
critical toxicity factors, data presentation and
qualifications, use of MC simulations in risk
characterization, selection of ground water data to
estimate the reasonable maximum exposure point
concentration, toxicity equivalency factors for
polycyclic aromatic hydrocarbons (PAHs), soil/dermal
adherence factors, midrange (CT) values for exposure
parameters, selection of COPCs, screening risk
assessment methods, and others.
RCRA
Limited guidance has been developed for conducting
various phases of a RCRA facility response action to
address current or past releases. The key RCRA guidance
documents that are available are identified below:
&
RCRA Facility Assessment Guidance (USEPA, 1986)
provides guidance for conducting facility assessments
to reflect developments of the RCRA corrective action
programs. Also clarifies the definition of SWMU.
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&
RCRA Corrective Action Interim Measures Guidance
(USEPA, 1988g) assists EPA regions and states in
performing corrective action interim measures to
mitigate or remove an exposure threat presented by
releases.
&
RCRA Corrective Action Plan (USEPA, 1988a)
provides technical framework for developing
corrective action orders and corrective action permit
requirements.
&
RCRA Facility Investigation (RFI) Guidance
(USEPA, 1989f) provides general guidelines for
performing health and environmental evaluations are
described in this four-volume guidance manual. With
regard to performing environmental risk assessments,
this guidance is substantively equivalent to RAGS and
references the CERCLA methodology.
1.6.4
State Requirements/Guidance. HTRW risk
assessors and PMs need to be aware of any risk
assessment procedures, data needs, or programs specific
to the state in which their site is located. Almost all states
have been authorized for RCRA permitting; some have
corrective action authorities. Many states have statutes
and regulations that address uncontrolled hazardous waste
sites and SWMUs associated with regulated RCRA
facilities. Also, many states have primacy in the water
pollution control program (under the CWA) and have
either adopted EPA criteria or developed their own water
quality standards. Many states have adopted the use of
risk assessment for corrective action to demonstrate "how
clean is clean," to develop site-specific cleanup goals, to
evaluate facilities burning hazardous waste, or for other
uses.
Some states (e.g., California and New York) have risk
assessment policies which may be interpreted as substantially similar to RAGS. Other states (e.g., Connecticut and
Kentucky) have adopted RAGS as a matter of policy.
Some states (e.g., Ohio and Massachusetts) have
developed formal risk assessment guidelines, ranging from
calculation of exposure point or background
concentrations to the adjustment of critical toxicity values.
Ohio and Tennessee recommend a health risk assessment
be performed for RCRA corrective action and closure to
demonstrate “how clean is clean.” Some states (e.g.,
Kentucky, Michigan, New
1-18
York, Oregon, and Texas) allow the use of risk assessment
to derive ACLs and medium-specific action levels or risk
reduction standards. A few states (e.g., Connecticut and
Illinois) have simple procedures in place (such as 20 times
the maximum concentration of contaminants for the toxicity
characteristics or use of equilibrium partitioning) to derive
preliminary soil/sediment cleanup levels. In general, risk
assessment or analysis procedures vary from state to state,
and sometimes within different departments or among state
agencies.
1.6.5
Others.
U.S. Army (USA)
AR 200-1 (USA) designates USACHPPM (formerly the
U.S. Army Environmental Hygiene Agency) to oversee and
recommend approval or disapproval on behalf of the U.S.
Army Office of The Surgeon General on all risk
assessments prepared by executing agencies for Army IRP
sites, Army BRAC sites, and FUDS. USACHPPM is the
DOD Lead Agent and Army liaison office for the ATSDR
program.
USACHPPM works with the military
components and ATSDR to prevent exposures at hazardous
waste sites and to prevent any potential adverse health
effects associated with such exposures. USACHPPM
executes the Memorandum of Understanding between DOD
and ATSDR, and identifies requirements and negotiates and
Annual Plan of Work with ATSDR.
U.S. Air Force (USAF)
The Office of the Air Force Surgeon General's Biomedical
Engineering Service (BES) is responsible for providing
technical support for all Air Force DERP CERCLA
activities. The Air Force Installation Restoration Program
Management Guidance (USAF, 1989) and Fiscal Year
(FY) 93/94/95 DERA Eligibility and Programming
Guidance (USAF, 1992) provide guidance in this area.
Work relating to hazardous waste management activities
under RCRA is performed by the BES in accordance with
Air Force Regulation 19-7 and USAF Hazardous Waste
Management Policy (USAF, 1991). Currently, the
environmental service centers for USAF, such as the Air
Force Center for Environmental Excellence, USACE, or the
risk assessors at respective
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Major Air Force Commands review risk assessments in
coordination with the Air Force Surgeon General.
U.S. Navy and Marine Corps
The Chief of Naval Operations directive OPNAVINST
5090.1B (DON, 1994), Department of the Navy (DON),
assigns command responsibilities and provides Navy
policy to comply with environmental laws and regulations.
The Navy and Marine Corps Installation Restoration (IR)
Program Manual (DON, 1992) describes the Navy
organization/responsibilities in support of IRP, priority for
funding, research, training, and reporting requirements
including preparation of Pollution Control Report to satisfy
the OMB Circular A-106 reports to EPA. The Naval
Environmental Health Center, under the direction of the
Bureau of Medicine and Surgery, provides a wide range of
medical consultative services to the Naval Facilities
Engineering Command community in support of the IRP,
the BRAC Program and other related environmental
projects. Consultative support services include but are not
limited to review of IRP and BRAC program documents
(e.g., work plans, sampling and analysis plans (SAPs),
quality assurance/quality control (QA/QC) plans; RI/FSs,
risk assessments, health and safety plans) from a risk
assessment and public health perspective; conducting risk
evaluations or quantitative risk assessments; training in
risk assessment, public health assessment, health and
safety plans, and risk communication; sponsoring the 3day tri-service Environmental Risk Communication and
Public Dialogue Workshop; negotiating with regulators
regarding the use of realistic exposure assumptions;
assisting in developing community relations plans;
assisting in establishing Restoration Advisory Boards;
assisting in preparing correspondence from a risk
communication perspective; preparing posters for public
exhibits and public meetings; acting as the DON liaison
for ATSDR issues.
USEPA
The USEPA has published a number of enforcement
policies and procedures for Federal facilities, e.g., Federal
Facilities Compliance Strategy (USEPA, 1988j),
Enforcement Actions Under RCRA and CERCLA at
Federal Facilities (USEPA, 1988b), Evaluation Process
for Achieving Federal Facility Compliance (USEPA,
1988c), Federal Facilities Negotiations Policy
(USEPA, 1989h), and Federal Facilities Hazardous Waste
Compliance Manual (USEPA, 1990a). All Federal
agencies are required to comply with hazards waste
regulations and the NCP in the same manner as the private
sector.
U.S. Department of Energy (DOE)
The DOE has issued a number of orders (5400 series and
others) addressing a variety of environmental statutes and
requiring all facilities to comply with the applicable environmental laws and regulations. For example, DOE Order
5400.2A (DOE, 1993) sets forth policy, direction, and
procedures for coordinating environmental compliance
issues and DOE Order 5400.4 (DOE, 1989) addresses
“CERCLA Requirements.” The Office of Environmental
Guidance of DOE has a plan in place to develop a
comprehensive guidance and training program for its field
facility staff and Environmental Restoration Project
Managers. In the area of risk assessment, the DOE
guidance or information briefs include: Integrated Risk
Information System (DOE, 1991), CERCLA Baseline Risk
Assessment (DOE, 1992a), and Use of Institutional
Control in CERCLA Baseline Risk Assessment (DOE,
1992b).
1.7 FEDERAL FACILITY AGREEMENT
Although there may be subtle differences between an FFA
and an IAG, these terms are used interchangeably under
CERCLA Section 120 which addresses both NPL and nonNPL sites. This section focuses on the need for early
planning and negotiation of an FFA among the USACE
customer (a Federal agency), EPA, and the state agency (as
appropriate). To accomplish this objective, the HTRW
project team member (i.e., the risk assessor) and others
should work cooperatively to develop statements/languages
or addenda to the FFA early in the HTRW project cycle to
define a flexible framework or process for RMDM and to
facilitate site closeout protective of human health and the
environment.
EO 12580 delegates DOD to conduct response action under
Section 104 of CERCLA (as amended by SARA) to address
releases on DOD facilities or originating from the facilities.
The order requires that the response action be conducted in
accordance with Section 120 of CERCLA. According to
CERCLA Section 120(e)(1), DOD is directed to enter into
an IAG with EPA for RA
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within 180 days of EPA's review of the RI/FS. In the
Federal Facilities Hazardous Waste Compliance Manual
(USEPA, 1990a), EPA states, "At a minimum, the IAG
must include a review of cleanup alternatives considered
and the remedy selected, a schedule for cleanup
accomplishment, and arrangements for operation and
maintenance."
statement may be entered which indicates the basis for
identifying IRA alternatives. This statement should address
the following:
&
The approach for conducting a screening risk analysis
of the Exposure Units (EUs) (USEPA, 1991a),
SWMUs, or the AOCs.
To address non-compliance issues at a Federal facility
(e.g., a DOD installation), EPA may issue a complaint
known as Notice of Noncompliance (NON). After such an
issuance, EPA and the Federal facility enter into
negotiation for a Federal Facility Compliance Agreement
which resolves compliance violations and stipulates
agreed-upon remedy, compliance schedule, and reporting
and record keeping requirements. The target date for
concluding such an agreement is within 120 days from the
date of NON issuance (USEPA, 1990a). Since RCRA
corrective actions are generally required at the time of
RCRA Part B permitting or permit renewal, the Federal
facility may be issued a RCRA Section 3008(h) corrective
action order rather than a NON.
&
The evaluation method for the risk assessment/analysis
results (qualitative or quantitative).
&
RMDM considerations (see Chapter 6) for identifying
and/or selecting the IRA alternatives.
"Executive branch disputes of a legal nature are properly
resolved by the President or his or her delegate..."
(USEPA, 1990a). In view of the above, and for the
purpose of this handbook, the risk assessor should provide
assistance to the USACE's PM, risk manager, and the
USACE customer so that an FFA or IAG can be
successfully negotiated to provide a framework for
RMDM and to initiate actions to protect human health and
the environment where these actions are needed. The risk
assessor and the HTRW project team may consider the
following areas for assistance to be provided to the
USACE customer concerning the FFA negotiation; these
areas have been identified in the DOD-EPA Model IAG
Language (USEPA, 1989h):
1.7.1
Basis for Interim Remedial Action (IRA)
Alternatives. For purposes of this guidance, IRA may be
interpreted as interim corrective measure under RCRA or
interim removal action under CERCLA. One purpose of
the FFA is to identify IRA alternatives which are
appropriate at the site prior to the implementation of final
RA(s). To identify such alternatives, the exposure area,
the exposure pathways which contribute to the principal
threat at the site, and the receptors/resources must also be
identified. For the purpose of the FFA, a
1-20
1.7.2
Requirements for RI/RFI and FS/CMS.
Another purpose of the FFA is to provide a framework for
investigating, assessing the impact, and evaluating remedial
options to protect public health and the environment. Such
a framework, consistent with the NCP and the RI/FS
guidance (USEPA, 1988i), may be modified and formally
incorporated in the FFA to meet the site-specific and project
requirements. Statements or languages or addenda to the
FFA may be prepared by the risk assessor and the project
team to serve as a basis for determining the extent of data
collection, data evaluation, assessment of baseline risk, and
evaluation of remedial alternatives. The HTRW TPP
process (USACE, 1998) and associated DQOs should be
identified as the framework for determining data needs, data
use, and quality. The point of departure for NFA and/or
monitoring only based on acceptable carcinogenic risk or
hazard should be identified in the FFA (USEPA, 1991a).
The statement should indicate the need for evaluating
uncertainties in risk assessment by the use of multiple
descriptors (i.e., RME, CT, population, and individual
risks). One important statement that should also be
considered for complex sites is the need for a probabilistic
risk assessment to identify the confidence level of
unacceptable risk or hazard, when the point estimate of risk
derived by the deterministic approach (e.g., RAGS Part A,
USEPA, 1989j) has marginally exceeded the acceptable
risk or hazard levels. These probabilistic risks (cumulative
function distribution) should be identified as an input into
the RMDM for these site actions.
1.7.3
Expedited Cleanup Process. Both DOD and
EPA are in agreement that early action or accelerated
cleanup may be needed to stabilize the site and to
EM 200-1-4
31 Jan 99
facilitate implementation of the final remedies. However,
the basis for such action is not well defined, except that the
actions are intended to control contaminant migration, to
reduce exposure, and to accelerate response. In addition
to time-critical and emergency response actions where
safety and acute hazards are involved, the risk assessor and
the project team can provide valuable input to the USACE
customer and risk manager for such expedited actions.
This can be rather quickly accomplished by comparing the
measured media concentrations with available human
health and ecological risk-based protective criteria. This
may be useful for relatively straight-forward sites, such as
drum removal, product removal, and containment. For
response actions at a complex site, a BRA may be more
appropriate, however, and expedited cleanup would not be
done. All decision criteria for eliciting response actions to
protect environmental components should be well thought
out, reasonable, and consistent with current EPA guidance.
1.7.4
Units Excluded from the Agreement. RCRA
and CERCLA integration issues should be addressed in the
FFA in unambiguous terms. This is particularly true for
sites of which the state agency is also an interested party or
natural resource trustee in the agreement. Some state
agencies have their own risk assessment policies and
guidance, and RMDM criteria which may vary
substantially from those of EPA (EPA's procedures under
RCRA and CERCLA are judged to be substantially
equivalent at this time). The risk assessor should review
state policies, guidance, and requirements, to identify any
critical risk assessment/risk management issues for the PM
and the customer for resolution. These issues should be
addressed and resolved in the FFA negotiations. If not
successful, separate FFAs may be needed to address
RCRA and CERCLA units within the facility. The
USACE and customer's legal counsels should be contacted
for briefing on these issues early in the process.
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CHAPTER 2
&
The HHRA provides a basis for comparing different
remedial alternatives.
&
The HHRA provides a consistent and widely accepted
methodology for assessing potential health risks, allowing for comparison of potential health risks between
sites.
2.0 PLANNING FOR AN HHRA
2.1 INTRODUCTION. The consistent standardized
approach presented in this guidance document was devised
to assure consistent treatment among sites. Numerous
other resource materials, guidance documents, bulletins,
memoranda, technical manuals, and books that address the
general HHRA approach and scoping of site-specific data
needs are available from EPA, other regulatory agencies,
and scientific sources. A number of these resources are
referenced in Appendix A. The generally accepted
approach to performance of an HHRA is presented in
RAGS (USEPA, 1989j), and a thorough understanding of
the process is prerequisite to working within the USACE
program. This guidance will not reiterate RAGS, but the
following paragraphs will provide the USACE risk
assessor and risk manager with the details necessary to
focus investigations toward site closeout and to provide
USACE policies and procedures on the HHRA process,
along with "how to" and "where to find" knowledge for
evaluating the scope, design, and conduct of a site-specific
HHRA.
2.1.1
Purpose of the HHRA. The HHRA is an
integral component of the PA/SI, RI/FS, RD/RA11, and
emergency response processes, serving multiple functions
in decision-making:
&
The HHRA provides an evaluation of the potential
human health risks under baseline (i.e., no action)
conditions.
&
The HHRA helps determine the need for RA at the
site.
&
The HHRA provides a basis for determining RGs for
chemicals in site media.
11
As stated previously, this document assumes the
processes involved in CERCLA and RCRA investigations
to be equivalent. For the rest of these discussions,
CERCLA terms only will be used. It may be assumed that
the procedures are also appropriate for the equivalent
RCRA phase.
2.1.2
Objectives of the HHRA. The goal of the HHRA
is to provide the necessary information to assist risk
managers in making informed decisions. The HHRA
provides important risk management input at various
project phases, identifying receptors or resources to be
protected, as well as limitations and uncertainty.
The HHRA should provide an objective, technical
evaluation of the potential impacts posed by a site, with the
risk characterization clearly presented and separate from
any risk management considerations. Although risk
assessment and risk management are separate activities, the
risk assessor and risk manager need to work together at
various stages throughout the project to define decision data
needs. In the HHRA, the risk assessor needs to present
scientific information in a clear, concise, and unbiased
manner without considering how the scientific analysis
might influence the regulatory or site-specific decision. The
risk assessor is charged with:
&
Generating a credible, objective, realistic, and
scientifically balanced analysis.
&
Presenting information on the problem, effects,
exposure, and risk.
&
Explaining confidence in each assessment by clearly
delineating strengths, uncertainties (as well as an
estimation of the effects of the uncertainties, both
magnitude and direction), and assumptions, along with
impacts of these factors (USEPA, 1995c).
The risk assessor does not make decisions on the
acceptability of any risk level for protecting the receptors or
selecting procedures for reducing risk. The HHRA is used
by the risk manager, in conjunction with regulatory and
policy considerations, to determine the appropriate response
actions at the site.
2.1.3
Minimum Requirements. The provision for
“minimum requirements” for the HHRA is an important
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31 Jan 99
concept. The risk assessor should identify particular
minimum requirements for activities preceding and used
in the HHRA to assure that critical factors are addressed.
Early in the process of planning the HHRA, the risk
assessor should also confer with the end users of the
assessment to identify all factors that need to be addressed
by the HHRA. The HHRA should be developed with its
end uses in mind. Early interaction with risk managers and
remedial designers is needed to obtain information on the
risk management options likely to be considered if RA is
required. This is not to infer that the HHRA should be
“tailored” to specific remedial options, for that would
compromise the objective nature of the assessment.
However, if the risk manager or remedial designer needs
certain information (for example, what depth of soil should
be considered surface soils, given projected site use or
exposure during remediation), the HHRA should provide
the basis that will allow this question to be answered
(within the appropriate boundaries of the HHRA).
2.1.4
Technical Requirements.
The technical
requirements of the HHRA should be considered early in
the site planning and investigative phase to assure that
appropriate information is gathered. It is important that
the risk assessor be involved in the early planning stages
of field investigations to develop the CSM, which will help
guide the identification of site media to be sampled, and to
assist in designing the chemical analytical scheme. The
risk assessor should also assist in DQO development for
performance-based methodology, design of the data review
process, and performance of the data useability
assessment. This will help assure that the best possible
and most relevant data are available for use in the HHRA.
2.1.5
Technical Basis. Risk assessments developed
for the various activities will have slightly different
requirements, require a different scope, and will involve a
different level of effort. However, the technical basis for
performing the risk assessment is essentially the same.
The main description of the risk assessment methodology
is provided below, and discussions of all types of risk
assessments are based upon this model. Therefore, the
information presented is necessary to the understanding of
other risk assessment applications. Each type of risk
assessment is discussed in subsequent chapters.
2-2
The HHRA is one component of overall site investigation
and remedial activities. It should be developed with a
recognition of how it is supported by preceding and
concurrent components of site activities, such as sampling
and analysis for the ERA effort, and how it supports and
shapes the subsequent components, such as RD. Although
the HHRA is performed to achieve several specific
objectives (describing current and future human health
risks), it needs to be coordinated with other site activities
(e.g., ERA) and needs to be responsive to other general site
concerns (e.g., restoration, mitigation, litigation) and the
resources (cost and schedule to be met) available.
The risk assessment process has been separated by
convention into four subdisciplines: hazard identification,
dose-response assessment, exposure assessment, and risk
characterization (NRC, 1983 and NRC, 1994). Hazard
identification is the process of determining whether
exposure to an agent could cause an increase in the
incidence of adverse health effects. The dose-response
assessment evaluates the relationship between the dose of
an agent and the probability of producing adverse effects.
Exposure assessment evaluates the combination of chemical
uptake and potential routes of exposure. Finally, risk
characterization summarizes and interprets the information
and evaluates the limitations and uncertainties in the risk
estimates (NRC, 1994).
Risk assessments have different applications in different
regulatory programs. This document discusses the
application of risk assessment in the following phases of site
activity:
&
PA/SI.
&
RI.
&
FS activities, including development of remediation
levels and comparative risk assessments associated
with selected remedial options, followed by the
evaluation of short term risks associated with the
implementation of the selected remedial option.
&
RD/RA activities, including potential need to further
evaluate short-term risks for the purpose of designing/
implementing control measures.
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31 Jan 99
&
Assessment of residual risk after implementation of
the selected remedial option.
2.1.6
Planning and Problem Identification.
Planning and problem identification are critical to the
success of the HHRA and its usefulness with respect to
remediation planning. To assure that the scope of the
HHRA is sufficient for making risk management decisions,
the risk assessor must always be mindful of the question,
"Do the data and approach support RMDM?"
In identifying data needs for the HHRA, the risk assessor
must fully understand the customer goals and the
regulatory program(s) driving the HTRW project
execution. The concept of TPP is fully explained in EM
200-1-2 (USACE), which emphasizes the need for the
data users (e.g., the risk assessor) to identify minimum
data requirements for the tasks to be performed.12 The
concept of "minimum requirements" for the HHRA is
important in that it identifies certain aspects for data
collection activities preceding the risk assessment to
assure that critical data gaps or factors are addressed.
The approaches and contents of the anticipated risk
assessment should be explained or discussed in the project
planning stage in unambiguous terms. An iterative, tiered
approach to the risk assessment, beginning with screening
techniques, is used to determine if a more comprehensive
assessment is necessary. The nature of the HHRA
depends on available information, the regulatory
application of the risk information, and the resources
available to perform the risk assessment. Informed use of
reliable scientific information from many different sources
is the central
feature of the process (USEPA, 1995a,c). The TPP process
should produce an outline for a site-specific HHRA that is
credible, objective, realistic, and scientifically-balanced.
Throughout the planning discussions, the risk assessor
should strive to point out potential setbacks, problems, or
difficulties that may be encountered in a "real world"
situation. When special circumstances (e.g., lack of data,
extremely complex situations, resource limitations, statutory
deadlines) preclude a full assessment, such circumstances
should be explained and their impact on the risk assessment
discussed. The risk assessor should also explain the
minimum data quality considered to be acceptable, how
non-detects will be treated, and how medium-specific data
will be evaluated or compiled to derive or model the
exposure point concentration in the risk assessment.13
2.2 PLANNING CONSIDERATIONS
2.2.1
Coordinating HHRA and ERA Planning.
Planning for a HHRA should be conducted concurrently
with that for an ERA in that these two efforts often have
similar data needs. Data needs for the ERA, however,
eventually focus on developing remedial alternatives that
are protective of ecosystem components, while the HHRA
focuses on developing remedial alternatives that are
protective of a single species, humans.
Coordinated planning efforts for the HHRA and ERA
efforts, particularly where there is to be an expedited
cleanup, should include consideration of the following:
&
Overlaps in information needs with regard to human
and ecological food chain issues.
&
Benefits of the cleanup and the effectiveness of
presumptive remedies.
12
The HTRW TPP process is a four-phased (Phase I
through Phase IV) process that begins with the
development of a site strategy and ends with the selection
of data collection options. Throughout the process,
USACE HTRW personnel of various disciplines and
responsibilities (some of whom may assume multiple
responsibilities) work closely together to identify data
needs, develop data collection strategy, and propose data
collection options for the customer. The HTRW data
quality design process implements the EPA's DQO
process, which is an iterative process applicable to all
phases of the project life cycle.
13
For example, if the RI data are skewed, it may be
necessary to address site risk by evaluating hot spots
separately. The risk assessor may wish to indicate this in
the Work Plan, in order to characterize hot spot areas
without delaying the assessment of risks for the non hot-spot
areas.
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31 Jan 99
&
Ecological impacts from removal or remedial
activities designed to protect human health.
&
Identification of hot spots that may impact both
human health and ecological receptors.
&
Identification of the key assumptions and criteria
common to the HHRA and ERA that may drive
cleanup decisions and focus the decision making
process.
&
Identification of areas of greatest concern that may be
addressed early as discrete tasks, thereby allowing
priority to be given to those (removal/remedial)
actions that achieve the greatest protection of the
environment and human health for the capital
(dollars) spent.
&
Activities common to both the human health and
ecological risk efforts that support DOD
responsibilities as a Natural Resource Trustee or help
coordinate between multiple Natural Resource
Trustees where jurisdictions or responsibilities
overlap.
2.2.2
Coordination with Natural Resource
Trustees. In the risk planning process, on Superfund sites
in particular, it is also important for the risk assessor, risk
managers, the technical team, and decision makers to
coordinate with natural resource trustees (e.g., DOD, the
state, the National Oceanic and Atmospheric
Administration [NOAA14], the U.S. Fish and Wildlife
Service, the U.S. Forest Service, and the Bureau of Land
Management) at the earliest possible stage. In this way, the
trustee can be assured that potential environmental concerns
are addressed, and conclusion of action may be expedited
(USEPA, 1989g, 1989h, and 1989i). Coordination with
natural resource trustee agencies such as NOAA provides
for the exchange of ideas and issues to assure the technical
adequacy of the RI/FS, to assure the protectiveness of the
selected remedy for trust resources, and to provide for
proper restoration and mitigation for injured resources.
Coordination also allows DOD access to the trustees'
specific skills, information, and experience.
This
interaction may occur through a variety of informal and
formal forums, including but not limited to: preliminary
scoping and drafting of work plans, review of final work
plans and subsequent data, technical review committees,
PM meetings, and public information meetings.
2.2.3
RAGS, Part D: Standardized Planning,
Reporting, and Review of Superfund Risk Assessments.
EPA Administrator, Carol Browner, called for an
improvement in the transparency, clarity, consistency, and
reasonableness of risk assessments (USEPA, 1995c).
Subsequently, the October 1995 Superfund Administrative
Reform #6A directed EPA to establish national criteria to
plan report & review Superfund risk assessments. As a
result, the Risk Assessment Guidance for Superfund
(RAGS): Volume I: Human Health Evaluation Manual;
Part D, Standardized Planning, Reporting, and Review of
Superfund Risk Assessments (USEPA, 1998a) was
developed. Additionally, EPA is developing standard
approaches for lead risks, radionuclide risks, probabilistic
analyses, and ecological evaluation that will be issued as
revisions to RAGS Part D.
14
NOAA's Coastal Resource Coordination Branch
(CRCB) works with EPA through all phases of the formal
remedial process at Superfund waste sites. The CRCB acts
for the Dept. of Commerce as trustee for natural resources
such as anadromous and marine fish. Coastal Resource
Coordinators (CRCs) and an advisory staff of
environmental, marine, and fisheries biologists provide
technical support and expertise to EPA, DOD, and other
agencies during response and cleanup at coastal waste
sites. The CRCs and supporting staff recommend
appropriate environmental sampling, coordinate with other
natural resource trustee agencies to build consensus on
natural resource issues, and recommend appropriate cleanup levels. The CRCB works with EPA to gain costeffective remedies that
2-4
The RAGS Part D approach includes three basic elements:
(1) Use of Standard Tools, (2) Continuous Involvement of
EPA Risk Assessor, and (3) Electronic Data transfer to
National Superfund Database. Brief descriptions of the
three components follow:
2.2.3.1 Use of Standard Tools. The Standard Tools
include a Technical Approach for Risk Assessment
minimize residual resource injury without resorting to
litigation. CRCs are in most EPA regions.
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31 Jan 99
(TARA), Standard Tables, and Instructions for the Standard
Tables. The TARA is a "road map" for incorporating
continuous involvement of the EPA risk assessor
throughout the CERCLA remedial process for a particular
site. The TARA should be customized for each sitespecific HHRA as appropriate. Electronic templates for
the Standard Tables have been developed in Lotus and
Excel for ease of use by risk assessors. For each sitespecific risk assessment, EPA recommends the Standard
Tables, related Worksheets, and supporting information
first be prepared as Interim Deliverables for EPA risk
assessor review, and should later be included in the Draft
and Final BRAs.
Instructions for the Standard Tables have been prepared
corresponding to each row and column on each Standard
Table. The Instructions should be used to complete and/or
review Standard Tables for each site-specific HHRA.
Instructions, example tables, and blank tables are available
for download at:
http://www.epa.gov/superfund/oerr/techres/ragsd/
ragsd.html.
2.2.3.2 Continuous Involvement of EPA Risk Assessors.
In this part of the document, the RPMs are instructed to
use the EPA risk assessors for all CERCLA sites, from
scoping through completion and periodic review of the
RA. It is stated that early and continuous involvement by
the EPA risk assessors should include scoping, work plan
review, and site-specific customization of the TARA for
each site to identify all risk-related requirements. It is also
emphasized that EPA risk assessors support reasonable
and consistent risk analysis and risk-based decision
making.
2.2.3.3 Electronic Data Transfer to a National Superfund
Database. Summary-level site-specific risk information
will be stored in a National Superfund Database
(CERCLIS 3) to provide data access and data management
capabilities to all EPA staff. These risk-related summary
data represent a subset of the data presented in the
Standard Tables. The electronic versions of the Standard
Tables (Lotus and Excel) are structured to be compatible
with CERCLIS 3.
2.2.3.4 RAGS Part D Applicability. The approach
contained in RAGS, Part D is intended for all CERCLA
risk assessments. Its use is also encouraged in ongoing
risk assessments to the extent it can efficiently be
incorporated into the risk assessment process. Part D is also
recommended for non-NPL sites, BRAC sites and RCRA
sites when appropriate. Chapter 1 of RAGS Part D
provides more detailed guidelines regarding the
applicability of RAGS Part D as a function of site lead and
site type. Each region will determine the site-specific
applicability, but USACE risk assessors should consider its
use on all HTRW projects.
2.2.4
The HTRW TPP Process. EM 200-1-2
(USACE) provides guidance on data collection programs
and defines DQOs for HTRW sites. DQOs define the
project's data needs, data use, number of samples required,
the associated QA requirements (e.g., quantitation
limits(QLs), blanks, split and duplicate samples, etc.), and
level of confidence or acceptable data uncertainty for the
requisite data. DQOs are generated at the final phase
(Phase IV) of the TPP process after the customer has
selected the preferred data collection program. The process
includes evaluation of previously collected data, and
assessment of the need for additional data to support the
current or subsequent phases of the project. This
coordinated TPP effort is designed to satisfy the customer
goals, applicable regulatory requirements, and minimum
technical data requirements for performing
site
investigations.
Throughout the process, USACE HTRW personnel of
various disciplines and responsibilities work closely
together to identify data needs, develop data collection
strategy, and propose data collection options. The HTRW
TPP process is consistent with the EPA's 7-Step DQO
process, which is an iterative process applicable to all
phases of the project life cycle. The DQO development
process is considered to be a Total Quality Management
tool (USEPA, 1989e). This is key to assuring successful
planning and performance of the risk assessment.
Phases I through IV (described below) of the TPP process
address site investigations methodically and should be
incorporated throughout the entire HTRW project life cycle.
Using this TPP process, the risk assessor will be able to
define minimum information requirements for risk
evaluations in support of site decisions.
2.2.4.1 Phase I - Develop Project Strategy. This phase of
the TPP process involves identifying site decisions
requirements and developing an approach to address these
requirements. Site strategy is broadly defined in the
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31 Jan 99
beginning of a project at this stage. As the project
progresses into subsequent phases, the strategy is refined
based on an improved understanding of the site. The risk
assessor is crucial to the development of appropriate site
strategy in this phase and the identification of data needs
and the associated quality requirements to support risk
management decisions. In this planning phase, site
conditions are reviewed qualitatively, and a preliminary
CSM is developed to help define the study elements for the
current and subsequent TPP phases.
2.2.4.2 Phase II - Identify Potential Data Needs. This
phase of the TPP process focuses on identifying data needs
and minimum data quality requirements to support site
decisions. Data users identify potential data needs and
their respective proposed QA/QC requirements based on
site background, regulatory information, and the
customer's goal. At this phase, the compliance, remedy,
and responsibility data users, who have specific data
needs, present their data requirements along with the data
needs identified by the risk assessor. The objective is to
identify the data needs and quality requirements of all
project team members.
2.2.4.3 Phase III - Identify Data Collection Options.
This phase of the TPP process incorporates previously
identified data needs and project constraints in designing
a data acquisition approach. Various sampling approaches
can be used, ranging from purposive (judgmental or
biased) to representative (random) sampling methods.
Additionally, various analytical schemes may be used such
as screening or definitive data. This phase of TPP also
involves identifying the optimum sampling/data collection
scheme so as to minimize mobilization, field sampling, and
demobilization efforts and costs. The objective of Phase
III is to identify options (preferably two or three options,
out of which one is an optimum option) for presentation to
the customer in Phase IV.
2.2.4.4 Phase IV - Select Data Collection Options and
Assign DQOs. This is the most important phase of the
TPP process because this is where the data collection
option is selected. To properly execute Phase IV, the
proposed options should be clearly explained and
characterized. The discussion should include data
uncertainties, cost/benefits, schedule, and other
constraints.
2-6
The product of this phase of the TPP process is the
Statement/Scope of Work (SOW) for USACE work
acquisition (either internal or the architectural-engineering
contractor), a detailed cost estimate (or Independent
Government Estimate) for the selected option, and DQOs
for the data collection program. The DQOs explain the
objectives of the data gathering activity, the data
type/location, data collection and analytical scheme, the
required QLs, rationale for requiring certain data quantity
and quality, and how the data are to be used in making site
decisions. Caution should be taken at this point about the
integration and coordination between the HHRA and ERA
as to how they influence DQOs. ERAs may require lower
media-specific QLs than HHRAs for certain COPCs
(Contaminants of Potential Ecological Concern for ERAs).
The ultimate DQOs should be the lower of either for dual
purpose samples, or the appropriate concentration for
specific purpose samples.
2.3 ESTABLISHING THE LEVEL OF EFFORT
An important part of planning for a HHRA is determining
the appropriate level of effort necessary to provide the
required information. As sites will vary in complexity, so
will the HHRA. Some of the site-specific factors affecting
the level of effort include the following:
&
The number and identity of the chemicals present.
&
ARARs, to-be-considered (TBC) criteria, and
applicable toxicity data.
&
Reasonable future site use.
&
The number and complexity of complete exposure
pathways and the need for fate and transport modeling
to establish exposure point concentrations.
&
The required QLs based on screening values and the
receptor populations.
&
Quality and quantity of existing analytical data.
The following sections present requirements for planning
risk assessment scopes of work for the various phases of
response. In addition to the evaluation of human health
risks, evaluation of the potential risks to ecological
receptors should be considered as well during the
EM 200-1-4
31 Jan 99
planning process, as duplication of effort needs to be
avoided. See the companion to this manual, EM 200-1-4,
Risk Assessment Handbook, Volume II: Environmental
Evaluation (USACE) for considerations necessary for
scoping an ERA. The following discussions will help
guide your data needs assessment but are not intended to
be all-encompassing. Data needs depend on the
complexity of the site, amount of useable data already in
existence, and site-specific receptors.
2.3.1
Preliminary Risk Screening; PA/SI. This
section focuses on data needs for the preliminary risk
screening in the site evaluation (site assessment) phase in
CERCLA and RCRA. Other HTRW site assessments,
although not specifically covered under these statutes, are
expected to be functionally equivalent.
2.3.1.1 Review of Existing Site Information. Before the
data needs for the PA/SI are conceptualized, the risk assessor should carefully review all site background
information. The data quality used to produce reports or
for proposed placement on the NPL (if available) should
be evaluated for this phase of execution, along with a
determination of whether additional data are needed. This
phase of investigation usually has little existing
quantitative information available. The purpose of this
review is to gain a good understanding on the following
issues:
&
&
15
Regulatory concerns or site problems relating to
human health to aid in preliminary identification of
significant
exposure
pathways
(source,
migration/transport mechanism, exposure routes, and
receptors).15
Physical characteristics and demographics of the site
which may help define possible pathways of
exposure.
In addition to the regulatory actions or concerns, the
risk assessor should also review any draft or final public
health advisories, e.g., the ATSDR health
consultations/advisories,
state
health/conservation
advisories on indigenous food sources, etc. The data
may be needed to accept or reject such advisories or
concerns. USACHPPM should be consulted on all these
public health matters.
&
Operational history with regard to site waste types,
probability of occurrence, and location of source areas.
This information will be valuable to begin to conceptualize
possible pathways of exposure and in determining data
needs to support the risk screening analysis.
2.3.1.2 CSM.
2.3.1.2.1
Data needed for the risk screening analysis
should be based on a preliminary CSM which is developed
in the absence of extensive site information. If there are
data available from a previous study, they should be
evaluated for useability in the risk screening, prior to
defining additional or supplemental data needs required in
the PA/SI. The CSM helps identify and visually organize
potential exposure pathways and receptors and identifies
those pathways which could be complete (significant or
insignificant) or incomplete, for the purpose of the data
needs determination. The elements of a CSM are:
&
Source of contamination (ground water, surface water,
soil/sediment, and air).
&
Potential release mechanism.
&
Migration pathways.
&
Potential receptors.
&
Major exposure routes (e.g., ingestion, inhalation,
dermal contact).
2.3.1.2.2
The risk assessor should begin to
conceptualize the data needs associated with each of the
aspects of the CSM that would support the screening risk
evaluation. For example, it may be determined that limited
judgmental sampling data can be used to conservatively
define source concentrations for direct contact exposure
point concentrations. A limited number of monitoring wells
may be sufficient to evaluate the ingestion route for ground
water. Additionally, the physical characteristics as well as
the demographics of the site are also helpful in the
evaluation of potential receptors and therefore complete
pathways to be evaluated in the risk screening analysis. All
parts of the CSM must be
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examined to ascertain that each element of potentially
complete exposure pathways has existing data that
adequately support each component of the risk screening
analysis.
2.3.1.2.3
Examples of general chemical data needs
according to source/route/receptor for use in assessing
potential exposure pathways for the risk screening are:
&
Surface soil (incidental ingestion/dermal contact and
inhalation of volatile organic compounds [VOCs] and
airborne particles).
&
Surface water (incidental ingestion/dermal contact).
&
Ground water (ingestion, dermal contact, and
inhalation of volatilized ground water contaminants
due to indoor use of ground water).
2.3.1.3 Identification of Data Gaps. Once all existing
data has been evaluated relative to the preliminary CSM,
the risk assessor can determine what data are required to
assure that the subsequent investigation can evaluate risks
due to all pathways identified as complete and significant.
Limited sampling of media expected to be impacted by site
operations can provide adequate information to eliminate
a site from further study. It is important to remember that
this phase of investigation does not attempt to determine
nature and extent of contamination, nor to determine the
magnitude of any potential risks present. The intent is to
determine whether the site poses no significant risk, and
may be proposed for NFA, or must be evaluated further.
This aspect is further clarified in Section 2.4.1.5.
subsequently evaluating the collected data to aid in making
informed site decisions at this stage of the HTRW response
process. This is justifiable if a weight-of-evidence
approach is used to support the evaluation and
recommendation. For example, the topography, visual
observations, history of spills, runoff pattern, and the
analytical results of purposive sampling would be sufficient,
as a whole, to support the argument whether contamination
of a medium is likely or unlikely.
2.3.1.4.2
For chemical data, however, the level of
confidence will be dependent on the QA/QC, sampling
method, sample handling/preservation method, analysis
method, and variability of the chemical concentrations in the
medium that was sampled. Reference the following EMs
for the requirements for the USACE chemistry program:
EM 200-1-1, Validation of Analytical Chemistry
Laboratories (USACE); EM 200-1-3, Requirements for
the Preparation of Sampling and Analysis Plans
(USACE); and EM 200-1-6, Chemical Quality Assurance
for HTRW Projects (USACE)16. The following factors
should be considered in this planning activity in order to
reduce uncertainties:
&
Analytical methods should be clearly stated that
identify the method DL and the QL. At a minimum, the
QL must be less than the action level to prove reliable
detections.
&
Level of QA - Depending on data use, the level of QA
for PA/SI can be field screening (i.e. screening-level
data) to assist identifying sampling locations, presence
or absence of contaminants with some confirmational
analyses, or confirmational analyses of chemical
identification and quantification, e.g., gas
chromatography/mass spectrometry method (i.e.,
definitive data).
&
QA/QC samples - Soil or sediment samples should
have field duplicates, laboratory control samples,
matrix spikes, and matrix spike duplicate samples.
Water samples should have field duplicates. In
addition, samples for the analyses of volatile and
semivolatile organic chemicals should be checked for
surrogate recovery. Laboratory blanks should also
2.3.1.4 DQOs:
Determining Data Needs and
Documentation. The level of effort is limited in this type
of assessment as is the amount of data needed to support
the screening.
2.3.1.4.1
In this step the general data needs defined
during conceptualization are formalized as data
requirements for each media type, specifying location of
sampling, depth of samples required, chemical analysis
requirements and corresponding DLs and QLs (based on
health-based screening levels for comparison), confidence,
and in some cases number of samples. The risk assessor
may consider a weight-of-evidence approach when
specifying data requirements and
16
EM 200-1-1 and EM 200-1-3 are currently in revision
and should be published in FY99.
2-8
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31 Jan 99
be analyzed to check for the presence of potential
laboratory contaminants.
&
Data variability - Detection of hot spots may not be
the objective of the sampling program under PA/SI.
The number of samples required to represent the level
of contamination with a predetermined level of
confidence will depend on the uniformity or
homogeneity of the contamination. This information
can only be obtained via historical documentation or
previous sampling events.
2.3.1.5 Risk Screening. The essence of the screeninglevel assessment is to determine if the site may be
eliminated from further concern or requires further study,
based on past releases, ARARs, and/or human health
impacts. The project study elements may include current
and future land use and the population characteristics,
based on the evaluation of the preliminary CSM.
However, this is a preliminary screening, and is intended
to be a conservative assessment of potential site risks.
Usually, the risk screening employs the highest detected
concentrations and compares them with health-based
screening levels, appropriate for the current and projected
future land use of the site. Generally, exceedance of these
conservative values is only an indication that further study
may be required, and does not indicate that risks are
significant, or that they even exist. See Chapter 6 for a
complete discussion of risk management issues
appropriate at this phase of investigation.
2.3.1.6 Reporting Requirements.
The following
elements should be clearly presented in the PA/SI Report:
&
Preliminary CSM, adjusted according to any new
information identified during the field investigation.
&
DQOs and an evaluation of whether or not they were
met.
&
The comparative risk analysis (the evaluation of
maximum detected values relative to health-based
screening levels).
&
Discussion of all uncertainties and their potential
impact on the results of the risk screen.
2.3.2
HHRA; RI. The sections below focus on
HTRW scoping for the baseline HHRA17 performed in the
RI. The purpose of the BRA is to estimate the degree of
risk associated with the site to human receptors in order for
an informed risk management decision to be made
regarding future actions. Generally, if the baseline risk is
acceptable, there should be little basis for the FS or RD/RA.
2.3.2.1 Review of Existing Data. At this project phase,
the risk assessor should have some understanding of the site
background and descriptions of site characteristics from the
review of the preliminary (PA/SI) data, contained in the
Federal Facility Docket or pertinent project files. This
information will be useful in focusing the data needs
required to prepare the BRA. Before the data needs are
determined, it is recommended that the risk assessor
carefully review all site background information and site
assessment reports, available state and/or EPA reports,
removal action information (if applicable), SI worksheets,
notes, or photos, etc. These studies, reports, and photos
help the risk assessor begin to focus on aspects of the site
which will require evaluation in the RI under the BRA.
2.3.2.1.1 Historical data collected for purposes other than
BRAs may be available from previous investigations,
facility records, permit applications, or other sources.
However, historical data sets may be limited by the lack of
information on laboratory and QA/QC procedures, or are
obtained from the wrong media and wrong location for use
in the BRA. Data from historical sources may or may not
be appropriate to use in the quantitative BRA and should be
reviewed for useability. When evaluating historical or
purposively collected data, a number of factors need to be
evaluated.
2.3.2.1.2 The review focuses on the following issues:
&
Regulatory concerns (or newly identified concerns)
relating to specific receptors, COPCs, and the
17
For the purposes of this text, Baseline HHRA and BRA
can be used interchangeably. BRA will be used here to
avoid confusion with established EPA guidance for HHRA
(USEPA, 1989j). It is understood that the evaluation of
potential environmental risks, or ERA, is an integral part of
the BRA.
2-9
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31 Jan 99
exposure pathways of concern, as well as those
pathways exceeding health-based screening levels in
the PA/SI screening-level HHRA.
&
Source areas which have been identified in previous
studies and the need for further quantification to
evaluate extent of contamination and risks.
&
Spatial relationships of pathways, and the need for
segregation as EUs or OUs to properly evaluate risks
to a number of receptor groups.
&
Possible transport pathways and available temporal
data, chemical/physical data describing degradation,
attenuation, or migration of chemicals in the
environment.
&
All possible current site receptors, including those
that may be considered sensitive, to begin grouping
by classification: agricultural, residential, etc.
2.3.2.2 CSM. The CSM is the basis for development
of the level of effort for the risk assessment and the DQOs
that will be defined in the SOW. The CSM presents
contaminant sources, release mechanisms, transport
media, exposure pathways, exposure points, and receptors
for current and future land uses. The CSM helps organize
and identify those pathways which are complete
(significant or insignificant) and incomplete. The risk
assessor should review site data and information collected
in the previous project phases (PA/SI) to refine the CSM.
The information should be able to assist the risk assessor
in developing a more definitive CSM or multiple CSMs if
there are multiple OUs. A CSM for ecological receptors
should be developed concurrently with the CSM. EM
200-1-4, Vol. II (USACE) describes this process. The
CSM for the BRA should help define and organize by
pathway:
&
Classes of COPCs (information concerning the source
characteristics, medium contamination, and
background chemicals is needed to identify COPCs).
&
Potential target media (ground water, surface water,
soil/sediment, and air).
&
Potential receptors exposed to the target media.
2-10
&
Major exposure routes or pathways of concern (e.g.,
direct contact resulting in soil or sediment ingestion or
dermal absorption of contaminants in the media,
consumption of food chain crops or species, ground
water ingestion, and inhalation of contaminants in
ambient air).
&
Migration and transport potential of site chemicals
from the source, including the effect of existing
institutional controls or removal actions (e.g., ground
water capture well systems).
&
Potential secondary sources of contaminants, and their
release/transport mechanism(s).
2.3.2.3 PRG Development. PRGs should be prepared or
obtained to assist in planning. PRG values will be used in
establishment of adequate QLs for the analytical scheme. In
order to characterize risks, QLs must be lower than the
PRG value used. Values developed by EPA Regions such
as Region 3 Risk-Based Concentrations (RBCs), or Region
9 PRGs may be used for direct comparison, or the risk
assessor may develop PRGs using default values for the
appropriate land uses for the site using methods described
in RAGS, Part B (USEPA, 1991d). Additionally, to
evaluate inter-media extrapolation, methods outlined in Soil
Screening Guidance: User’s Guide (USEPA, 1996b) and
Soil Screening Guidance: Technical Background
Document (USEPA, 1996a) may be used.
2.3.2.4 Identification of Data Needs. During the review of
background information, the risk assessor will likely notice
that there is limited data and information available from
previous investigations, and that additional data must be
collected in the RI to support a BRA. The technical team
should note data gaps that exist and will need to be
considered in the development of the data collection
strategy for the RI. Common data gaps may include
insufficient characterization of nature and extent of
contamination to adequately describe an exposure pathway,
insufficient background characterization, and insufficient
sample number to determine a 95% Upper Confidence
Limit (UCL) of the mean concentration for an exposure
area.
The data needs for an RI focus on addressing the nature and
extent of contamination, potential migration, and possible
receptors available to complete the exposure
EM 200-1-4
31 Jan 99
pathways. Guided by the CSM, different types of data may
be needed to address requirements and objectives of the
BRA.
&
Data or information in support of determining current
and future land use and population characteristics.
.
&
Data
to
support
fate
and
transport
modeling/calculations (total organic carbon, grain
size, porosity, processed meteorological data, etc.).
&
Data to conduct qualitative and/or quantitative
evaluation of uncertainties in the risk assessment
(mean, maximum, minimum, or the entire distribution
of values for key parameters identified by a sensitivity
analysis).
&
Data to support qualitative assessment of potential
receptors and populations (census information,
postal-carrier route information/DataMap®, etc.).
&
Toxicity data to assess risk or hazard. Where critical
toxicity values are not available from EPA, the
appropriate DOD Toxicology and Research Program
offices may be consulted (e.g., USACHPPM
Toxicology Directorate at: http://
chppm-www.apgea.army.mil/tox/program.htm
then contact the Health Effects Research Program
Manager; or contact the Air Force Research
Laboratory, Human Effectiveness Directorate,
Operational Toxicology Division, at:
http://voyager.wpafb.af.mil or (937) 255-5150
x3105).
&
Representative data for evaluating the nature and
extent of source and pathways, with appropriate
confidence for intended data uses, and background
chemical concentrations.
2.3.2.5 DQOs. The quality of a BRA is directly
dependent upon the quality of the chemical data applied.
Regardless of how well other components of the BRA are
performed, if the quality of the data is poor or the data do
not accurately reflect the site contamination or the types of
exposures assessed, the BRA will not provide an adequate
description of potential health effects posed by the site.
Therefore, it is imperative that
the types of data scoped for use in the assessment be
carefully planned.
2.3.2.5.1 Planning for appropriate data acquisition is an
important step in obtaining data of the necessary quality.
During this planning stage, appropriate location, numbers,
and types of samples, DLs and QLs, and analytical
requirements can be specified as part of the DQO process.
These and other specific minimum requirements for BRA
data should be specified prior to data collection by the
technical team in early stages of site planning or scoping.
Once available, a thorough review of the resultant data is
needed to assure that the DQOs have been met (see section
4.2). This further assures that the most appropriate
information is used in the BRA.
2.3.2.5.2 The risk assessor should begin to document data
needed, identifying data types, location, quantity, and quality
requirements. Chemical data to be collected should be
identified with the appropriate QA/QC requirements. See
Guidance for Data Useability in Risk Assessment (Part A)
(USEPA, 1992h). In addition, the level of confidence
(maximum error rate) required of the sample results should
be set, after considering the potential variability of the
sample results in a given matrix and potential
laboratory/sampling handling errors. For nonchemical
types of data, the QA requirements will be established on a
case-by-case basis. At a minimum, the source of
nonchemical data and an assessment of their reliability and
representativeness for use at the site should be documented.
2.3.2.5.3 The analytical methods applied to BRA data
collection should be specified as part of the minimum
requirements prior to the data collection. Once data results
are available, the analytical methods used and DLs and QLs
attained should be reexamined to identify any deviations
from the minimum requirements, and the impact of that
deviation upon data useability.
2.3.2.5.4 Three broad types of analyses are available, each
having a different potential use in a BRA:
&
Field screening data, such as those collected with
direct-reading or field instruments (photoionization
detectors, combustible gas indicators, or field
chemistry tests). Because of the uncertainty associated
with these methods (due to lack of stringent QA/QC
protocols), these data are best used
2-11
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31 Jan 99
qualitatively or in conjunction with verified results by
more reliable methods unless the method can demonstrate
equivalency with a proven method.
&
&
Field laboratory analyses, such as those obtained from
a mobile onsite laboratory. These data can be used in
a BRA if appropriate QA/QC procedures have been
followed and the data are of good quality, as determined by the data evaluation process.
Definitive data. These data are appropriate for
inclusion in a BRA if appropriate QA/QC procedures
have been followed and the data are of good quality,
as determined by the data evaluation process.
2.3.2.5.5 Several different laboratory analytical protocols
are available, varying in the instrumentation, the level of
QA/QC, sensitivity, QLs, and other factors. EM 200-1-3
(USACE) presents summaries of common analytical
methods and identifies the instrumentation and DLs/QLs
for different analytes. This resource should be consulted
when choosing analytical methods to quantitate data for
use in the BRA.
2.3.2.5.6 Two analytical protocols that are commonly
applied to environmental sampling are the EPA's SW-846
protocol and the Contract Laboratory Program protocol.
To give the USACE programs the greatest flexibility in the
execution of its projects, the SW-846 methods, as
published by EPA, are generally the methods employed for
the analytical testing of environmental samples. These
methods are flexible and can be readily adapted to
individual project-specific requirements (USACE, 1994b).
2.3.2.5.7 The minimum requirements for planned BRA
data collection should also specify the QLs to be attained
in the chemical analyses. The limits should be low
enough to enable quantitation of chemicals below concentrations of potential health concern. QLs are generally
specified by the analytical method; however, deviations
from planned QLs can occur as a result of matrix
interferences, high chemical concentrations, laboratory
variations, and other factors.
2.3.2.5.8 When selecting QLs the risk assessor and
project chemist should consider that EPA risk
2-12
assessment methodology specifies that one half the sample
QL should be used as the proxy chemical concentration if
there is reason to believe that the chemical may be present
on the site. Appropriate QLs can be determined by an
evaluation of health-based screening levels for site
chemicals (see paragraph 2.4.2.3).
2.3.2.5.9 Data quality. For chemical data, the level of
confidence will be dependent on the experience and the
ability of the laboratory to be able to deliver quality data,
associated QA/QC, and variability of the chemical
concentrations in the medium that was sampled.
Coordination between the risk assessor and project
chemist/data reviewer is recommended in order to design
the sample collection program which is most likely to
produce sample results with an acceptable level of
confidence, considering such factors as laboratory QA/QC,
level of QA required for the data, QA/QC samples, and data
variability. Sensitivity requirements should be identified in
this scoping phase so that the data collection program will
minimize the degree of uncertainty.
2.3.2.5.10
The output of the data planning discussed
above should be a SOW section and/or data needs
worksheets. The purpose of documentation, as well as
communication with the other team members, is to avoid
potential misuse of data or the risk assessment results,
making sure that the selected data collection option meets
the users' and decision-makers' needs. In particular, the risk
assessor should explain the minimum data quality
considered to be acceptable, how nondetects are treated,
and how medium-specific data are evaluated or compiled to
derive/model the exposure point concentration in the risk
assessment. If a health assessment, health survey, or
epidemiological study is to be performed by the ATSDR,
the risk assessor should (in coordination with USACHPPM
for Army IRP and FUDS projects) indicate in the summary
or outline how the data are to be used, evaluated, or
interpreted.
2.3.2.6 Reporting Requirements. The risk assessor should
define the minimum requirements associated with each of
the following elements. Specification of these project study
elements and minimum requirements should be recorded in
the SOW. Defining minimum requirements will also add
more specificity to the CSM
EM 200-1-4
31 Jan 99
development, allowing for easier determination of the data
needs.
&
Data evaluation - COPC selection, defining
site-related chemicals, and nature and extent of source
areas.
&
Exposure assessment - pathway evaluation, fate and
transport of contamination, exposure point
concentration, and intake assessment.
&
Toxicity assessment - determination of toxicity values.
&
Risk characterization - calculation of risks.
&
Uncertainty analysis - quantitative and qualitative
documentation of uncertainties associated with each
phase of the study.
2.3.3
Risk-Based
Analysis
of
Remedial
Alternatives; FS. The scoping requirements for the FS
focus on evaluating the potential alternatives for their
effectiveness in reducing the baseline site risk. Data are
needed to assess any short-term or long-term risks (if the
RA lasts a duration in excess of 7 years).18 It should be
noted that many sites are required to have the RI and FS to
be conducted simultaneously. Therefore the preparatory
steps for conceptualizing data needs between RI and FS
are comparable and will not be reiterated here.
Risk aspects of the FS are three-fold:
&
Development of site-specific cleanup levels for
screening remedial alternatives and consideration for
adoption as RAOs.
&
Evaluation of potential remedial alternatives for their
abilities to meet RAOs.
&
Assessment of the fate and transport mechanisms of
any potential release or discharge of the media being
remediated or treatment byproducts/ residues.
18
The 7-year period has been suggested by EPA as the
point of departure between short-term (subchronic) and
long-term (chronic) risks.
In addition to evaluating the alternatives for
“protectiveness” of human health and the environment, the
risk-based evaluation of remedial alternatives must consider
risk and toxicity reduction, interruption of the exposure
pathway(s) shown to pose the principal threat in the BRA,
and the post-remediation (residual) risk.
2.3.3.1 Review of Existing Data. At this project phase,
the risk assessor and the project team should have a good
understanding of the nature and extent of contamination. In
addition, they will also have a good understanding of the site
strategy and customer's goals and concept of closeout. In
reviewing the background information, the risk assessor
should note the AOCs requiring remediation, and the
location of these areas relative to future as well as current
onsite and offsite populations. Census projections and other
demographic information should be reviewed. Locations of
sensitive populations (nursing homes, nursery schools, etc.)
should also be noted. The background information review
may also identify issues of concern, for example:
&
Previous or newly identified regulatory concerns
relating to residual risks (risk remaining upon
completion of selected remedies and/or proposed
removal actions).
&
Project status with respect to decision path leading to
site closeout if the selected alternative is not effective
or fully implemented.
&
Customer's goals and objectives, plan of action,
budget/time constraints for RD/RA, removal actions,
and the 5-year review, if applicable.
2.3.3.2 CSM. The refined CSM developed for the BRA
will be reevaluated in the FS scoping phase to account for
pathways which reflect post-remediation conditions as well
as pathways that may become available during remediation.
Two CSMs may be developed for each remedial alternative:
(1) the CSM during remediation; and (2) the CSM for the
site after remediation has been completed. The former is
used to guide data needs to assess short-term risks (or longterm risks if the period of remediation is in excess of 7
years); and the latter, to guide data needs for the degree of
risk reduction or the post-remediation risk. The exposure
pathways of concern for the short-term risk CSM are
primarily air (fugitive dusts or VOC emissions) and
discharge of treated effluent
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31 Jan 99
to ground water/surface water. It should be noted that
neither of these evaluations requires an assessment of the
net environmental benefit if offsite treatment/disposal is
the alternative to be evaluated.19 Therefore, the risk
evaluations under FS are limited to impacts on human
receptors who reside onsite or near the facility, and
residual risks to receptors after implementation of the
alternative. It should be noted that control measures
required to mitigate short-term risks associated with
remediation should be conducted in the RD/RA stage.
2.3.3.3 Identification of Data Gaps. It should be noted
that this stage of HTRW project planning should focus
primarily on the two questions: “What is the degree of risk
reduction offered by the remedial alternative?” and “What
are the potential short-term and long-term risks (if
applicable) associated with implementation of the
alternative?” Guided by the CSMs, data may be needed
for all or any one of the following risk assessment tasks to
assist in the selection of a remedial alternative:
&
Data to support fate and transport modeling (e.g.,
grain size and processed meteorological data);
&
Data to conduct qualitative and/or quantitative
evaluation of uncertainties in the risk assessment
(mean, maximum, minimum, or the entire distribution
of values for key parameters identified by a sensitivity
analysis). It should be noted that this level of effort is
generally not required except for onsite incineration.
&
&
Data to assess risk or hazard to receptors (rate,
concentration, chemical identity, and toxicity) of
emissions or treatment products/residues which may
be released during remediation.
(ingestion of and dermal contact with ground water,
inhalation of airborne contaminants, etc.) which were
identified as data gaps in the previous step. SOW sections
should be prepared to document required data types, locations, and quality requirements. Chemical data to be
collected should be identified with the appropriate QA/QC
requirements. In addition, the level of confidence
(maximum error rate) of the sample results should be
defined, after considering the potential variability of the
sample results in a given matrix and potential
laboratory/sampling handling errors. The emission or
discharge data may be obtained by modeling or from the
results of a performance test of the full-size model or a
pilot-scale model.
2.3.3.5 Risk Calculations: RAOs and RGs. RAOs consist
of medium-specific RGs, modified from PRGs during or
after the BRA, to assure protectiveness of human health and
the environment. The final modification to the PRGs
calculates allowable media concentrations from the
acceptable risk levels determined through the risk
management process. RAOs should be expressed as both
a contaminant level and an exposure route, as
protectiveness may be achieved by either reducing the
contaminant level, or by reducing or eliminating exposure.
Coordination of this process with the RAOs/RGs developed
during the ERA is critical to assure that the selected remedy
is protective of both human and ecological receptors.
2.3.3.6 Reporting Requirements. The requirements to be
reported in the FS are summarized and identified below:
&
Development of RGs, presented in the RAOs section.
&
Assessment of RAO protectiveness, given the
acceptable risk range and uncertainties in deriving the
RGs, background concentrations, and the analytical
DLs. Presented as part of the screening of alternatives
section.
&
Assessment of long-term effectiveness/residual risk to
human health and the environment (evaluate if risk
reduction afforded by the proposed remedial
alternatives is effective). Presented in the detailed
analysis of alternatives section.
Data on the treatment byproducts and residues.
2.3.3.4 DQOs. This step defines the specific data
requirements according to potential exposure pathways
19
EPA has implemented an off-site policy (USEPA,
1993a) requiring the facility receiving environmental
debris or media for treatment or disposal be either in
compliance with RCRA Subtitle C or under a scheduled
compliance action or corrective action.
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&
Assessment of short-term effectiveness (evaluate if
the proposed remedial options pose unacceptable
short-term risks to humans onsite and offsite during
the RA. Presented in the detailed analysis of
alternatives section.
2.3.4
Short-Term
Risks
Associated
With
Construction. This section focuses on HTRW data
scoping for the evaluation of control measures needed to
mitigate short-term risks posed by construction of
CERCLA removals or RAs. To meet the risk assessment
or evaluation data needs, the risk assessor should
coordinate with the PM, as well as other data users to
identify the remedy aspects which require risk evaluation
in this phase.
As a screening or comparative risk analysis has already
been performed in the RI/FS project phase (or an EE/CA
for a non time-critical removal action), performance of risk
assessment tasks in this phase is generally limited in scope
(unless there is a need for a more detailed risk assessment
because the construction is likely to result in a significant
release of site COCs). If this is the case, information from
previously performed risk analyses should be reviewed
and additional data needs identified as required. Risk
assessment of removal actions or construction of the
selected remedial alternative should generally follow
procedures and data requirements described in RAGS Part
C (USEPA, 1991e).
When evaluating data needs and their quality/quantity,
consideration should be given for completing the
evaluation in a timely manner. Striking a balance between
the desire for site-specific/treatability data and assumed
data (data from other sites) for use in the evaluation is the
key aspect in this project planning stage. Other areas for
project planning that may require coordination between the
risk assessor and other project team members (e.g., the
health and safety specialist) are:
&
&
Short-term impact of the remedial alternatives on site
environment (i.e. acute risks to ecological receptors
or habitat destruction, or risks to surrounding human
populations and/or on-site remedial workers).
Risk of accidents during construction (physical
hazards, explosions, spills, etc.).
&
Risk communications (public perception
understanding of risks from the alternatives).
&
Other risk management considerations or criteria (e.g.
cost,
schedule,
operations
and
maintenance/engineering and operational flexibilities,
etc.).
and
2.3.4.1 Review of Existing Data.
The information
developed in the FS in conceptualizing data needs to assess
the short-term risks can be used to develop or revise the site
strategy. It is recommended that the project team carefully
review all site background information, RI and FS reports,
and any pertinent field tests or studies.
Through qualitative or quantitative risk assessment or
analyses, a determination will be made as to whether or not
additional controls are needed to address risks during
remediation or the residual risks. If the assessment
indicates any unacceptable potential risks, the decision will
focus on: (1) whether the selected remedy can be
implemented under the design and operation plans without
posing an unacceptable short-term risk or residual risk; (2)
the need for removal actions to reduce the threat of human
health risks or expedite/enhance site remediation; and (3)
control measures (operational or engineering) to mitigate
site risks and to assure compliance with ARARs and TBC
requirements. Therefore, specific decisions associated with
this executable project phase may include all or any combination of the following:
&
Determine whether the selected remedial or removal
actions are likely to comply with Federal and State
ARARs or TBC health-based criteria required by the
agencies regarding short-term risks.
&
Determine if additional control measures are required
to be designed and implemented to mitigate or reduce
short-term risks (or if new remedies should be
recommended to replace the selected remedies).
&
Determine if removal actions are needed to mitigate
imminent threat to human health and environment.
&
Determine if the selected removal actions are
consistent with the final site remedy (if such remedy is
reasonably expected).
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2.3.4.2 CSM. Data needed for evaluation of controls to
reduce short-term risks associated with remediation should
be based on the CSM developed in the FS, focusing on the
potential impact of the remedy to receptors identified, and
the effect of control measures. The data needed may be
nonchemical in nature, e.g., engineering design parameters
to reduce, remove, or change the physical/chemical nature
of the emission, effluent discharge, or residues. The
sources of these data may be the remediation
vendors/contractor, EPA's literature (e.g., feasibility
studies under the Superfund Innovative Technology
Evaluation [SITE] program), or design information from
other sites using the same/similar technology and wastes.
The data needed may also be chemical in nature, e.g.,
constituent concentrations in the emissions or discharge,
or the chemical identity, toxicity information, quantity, rate
of release, and fate and transport characteristics of
treatment byproducts, derivatives, or residues.
The CSM should be appropriately modified to help the
project team focus the data collection effort to evaluate
significant pathways for potential emission or discharge
during the remediation period. The CSM focuses on the
source, release, fate and transport, and exposure point
concentration, routes and receptor to aid the risk
assessment.
2.3.4.3 Identify Data Gaps. It should be noted that data
needs at this stage of the HTRW project planning should
primarily focus on the project decision: “What control
measures are required to mitigate the short-term risk to the
appropriate human receptors onsite and/or offsite
(individuals and community)?” If the RA requires
transportation of wastes offsite through areas of dense
populations or congested transportation routes, evaluation
of controls required to eliminate potential risks of
accidents/spills associated with this offsite action may also
be required. The risk assessor should coordinate with the
health and safety specialist, design engineer, and chemist
to define data quality and quantity, and locations of
samples.
Guided by the CSM, data may be needed for all or any one
of the following risk assessment/evaluation tasks to
respond to the project decision on whether or not there is
a need to impose control measures; augment or modify the
selected remedy; or conduct removal actions:
2-16
&
Evaluate in more detail the short-term risk
assessment/analysis performed for the FS to reduce
uncertainties; some of the data requirements may be:
-
Data to support fate and transport
modeling/calculation, e.g., grain size of soil
handled, residue or solid waste stream leaching
characteristics, processed meteorological data, etc.
-
Data to assess the amount of discharge or
residues, e.g, amount of soil re-suspension for a
specific soil handling method, estimation of
fugitive dust volatilization, stack gas emissions, or
effluent discharge rates, etc. (i.e., representative
monitoring or field data to assess risks and
demonstrate compliance with protective
criteria/standards are needed).
-
Data to support qualitative assessment of potential
exposure to receptors and populations (method of
residue disposal or environmental media into
which effluents/emissions are discharged,
transportation routes for wastes to offsite
locations, population or census information, etc.).
-
Data to assess risk or hazard (toxicity information
of waste residues, byproducts, derivatives, and
degradation products (for bioventing or
bioremediation)).
-
Data to compare ARARs and TBC short-term
health goals with representative site sample or
monitoring data which meet predefined QA/QC
criteria.
2.3.4.4 DQOs. This step defines the data types required
according to potential exposure pathways. Examples of
data types according to medium for use in assessing
potential exposure pathways are: incidental ingestion or
dermal contact with the treatment residues or effluent and
inhalation of airborne particles or volatilized organic
chemicals. In each of these data types, sample data or
continuous monitoring data, and data for modeling the
exposure point concentration for the site contaminants or
their treatment derivatives/residues in the media may be
needed.
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To evaluate the need for control measures for the selected
remedial alternatives under this project phase for shortterm impact during remediation and residual risk after
remediation, data relating to the design, operation, and
maintenance of the remediation system are needed to
calculate the discharge or release rates of the site
constituents and the process waste streams. The process
waste streams include chemical characterization of all
remediation or treatment byproducts, derivatives, or
residues during and after remediation, which may impact
onsite and offsite humans. It should be noted that the
screening or comparative assessment of remedies for
short-term risks should have been conducted in the FS
stage, before remedy selection, and in this phase a more
rigorous analysis of risks and control measures are
developed for the selected alternative. The data quality
used in these screening analyses should be reviewed to see
if they meet the data user's requirements.
2.3.4.5 Reporting Requirements. The following presents
the elements which address different aspects of controls to
reduce short-term risks within the design analysis for
construction of removal actions or RAs.
&
The evaluation of potential control measures
necessary to mitigate risks associated with remedial
or removal actions; usually part of the design analysis
included in the RD.
-
Health and safety design analysis; engineered
barriers, monitoring, worker protection, and
response measures.
-
Environmental controls and permitting; dust
control, air emission control, effluent and runoff
controls.
-
Methods of construction; excavation, grading,
structure construction, etc. and control features
associated with each.
-
Phasing of construction.
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CHAPTER 3
3.0 EVALUATING
HHRA
THE SCREENING-LEVEL
3.1 INTRODUCTION
HHRAs performed at the PA/SI stage are typically
screening-level in nature and are performed to identify
whether a site needs to be assessed further or can be
eliminated from further concern. Rarely would a
screening-level HHRA provide adequate information to
justify remediation. Since the information that is available
at this point of a site response is usually limited, a
conservative approach is used in performing the
assessment.
3.2 SCREENING-LEVEL HHRAs
The basis of the screening-level HHRA is a comparison of
site media concentrations (typically, the maximum
detected concentration is used) with health-based
screening levels, calculated according to RAGS protocol.
The recommended values to use for performing this
evaluation are those developed by EPA Region 3 (RBC
Tables) or Region 9 (PRG Tables), both updated regularly.
It is important to note that the RBC and PRG values noted
above are not equivalent, as the exposure pathways
evaluated are different. Therefore, it is imperative that
these values be applied within the context that they were
developed. The basis for utilizing these values will be
introduced later in this chapter, and presumes an
understanding of general risk assessment methodology.
PRGs are not synonymous with RGs. For a complete
discussion of the development of site-specific PRGs, and
appropriate methodology for calculation of RGs, see
RAGS Part B (USEPA, 1991d).
3.2.1
Chemical Data Collection and Review. In
order for the screening-level HHRA to achieve the desired
objectives, the data applied to the assessment must be
appropriate for the intended use. Data that are available
from PA/SI activities are usually limited in number, but
should be broad in scope of chemical analysis and in the
type of media sampled.
3.2.1.1 An important component of the data review for a
screening-level HHRA is an evaluation of the
representativeness of the data. Sampling should have been
conducted in areas of suspected contamination in order to
provide information on the “worst case.” If sampling was
not conducted in areas of suspected contamination, the
screening-level HHRA will not provide an adequately
conservative assessment of potential risks. Similarly, if a
broad chemical analysis was not performed, or if data are
not available for all media of potential concern, the
usefulness of the screening-level HHRA will be limited and
would not be appropriately used to eliminate a site from
further consideration.
3.2.1.2 The following factors are minimum requirements
for data used in a PA/SI screening-level HHRA:
&
Chemical-specific analysis of all environmental media
of potential concern (e.g., soil, sediment, surface water,
and ground water).
&
A broad chemical analysis (or defensible historical
information regarding specific COPCs).
3.2.2
Exposure Assessment. Two primary elements of
the screening-level HHRA for a PA/SI are the identification
of the appropriate receptor group(s) and selection of
appropriate exposure point concentrations.
3.2.2.1 Selection of the population group with the highest
potential exposure is required in applying the appropriate
health-based screening values. Development of the
preliminary CSM can be used to identify this group. The
EPA regional health-based screening values are based on
either residential or occupational exposures.
3.2.2.2 As a rule, the highest detected chemical
concentration in a medium is compared with the healthbased screening value. However, the range of chemical
concentrations detected, as well as the number of samples
collected, should be reviewed to determine whether this
approach is appropriate. If the screening level HHRA does
not provide a clear determination of whether the site can be
eliminated from further consideration, further study under
an RI (i.e., BRA) is indicated.
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3.2.3
Health-Based Screening Levels. As noted
earlier, the health-based screening levels calculated by
Region 3 and Region 9 are not the same, as they evaluate
different exposure pathways. The pathways evaluated are
delineated as a lead in to the tables. Note that these values
are updated regularly, and care should be taken to assure
that the most recent values are used. The Region 3 RBC
tables can be accessed on the Internet at
http://www.epa.gov/reg3hwmd/risk. The Region 9 PRG
tables can likewise be accessed at:
http://www.epa.gov/region09/waste/sfund/prg/index.htm
To appropriately use the health-based screening values,
the risk assessor must be aware of the assumed exposure
pathways and exposure factors used to derive these values.
If exposure pathways other than those used for the
calculations are anticipated to be significant at a given site,
use of the health-based screening values is limited. Other
values, developed by other EPA regions may also be
appropriate, particularly if the site where the assessment is
performed falls within that geographical region.
3.2.4
Risk Screening. To perform the risk screening
in a PA/SI, the maximum chemical concentration in each
medium is compared with the selected health-based
screening level. In general, if the maximum chemical
concentration exceeds the health-based screening level,
further study of the site is indicated. The range of
chemical concentrations detected, the degree of the
exceedance of the health-based screening level, and the
appropriateness of the value itself should be evaluated as
part of the decision-making process in determining
whether the site should be eliminated from further concern
or if further study is warranted.
3.2.5
Characterization of Uncertainty.
The
uncertainties associated with a screening-level HHRA
should be clearly presented as part of the assessment. The
potential effect of the following factors should be
discussed:
&
Uncertainties associated with the limited chemical
data base for the site.
&
Use of maximum chemical concentration for
representing exposure at the site.
&
Use of highest exposure or “worst case” receptors.
3-2
&
Application of the health-based screening value and the
inherent assumptions used in its derivation.
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CHAPTER 4
identifying the factors that should be present in a wellconstructed risk assessment.
4.0 EVALUATING THE BASELINE HHRA
4.1 INTRODUCTION
This chapter presents the conceptual and technical
objectives for evaluation of a baseline HHRA20, and the
minimum content expected to be included when evaluating
a BRA. The BRA provides an objective technical
evaluation of the potential health impacts posed by a site
and should not incorporate policy, management, and other
nontechnical factors. The BRA should be clear about the
approaches, assumptions, limitations, and uncertainties
inherent in the evaluation to enable the risk assessor and
risk manager to interpret the results and conclusions
appropriately. The BRA is used by the risk manager, in
conjunction with regulatory, policy, feasibility, schedule,
budget, and value of resources considerations, to
determine the appropriate response actions at the site.
The BRA is one component of overall site investigative
and remedial activities and, as such, should be developed
with an understanding of how it is supported by preceding
components of site activities, such as sampling and
analysis, and how it supports and shapes follow-on
components, such as remediation. Although the BRA is
performed to achieve several specific objectives (such as
describing potential health risks), it may also be needed to
support other general response objectives.
This chapter is not intended to be a step-by-step
instruction manual for developing a BRA, rather, it is a
guide for reviewing and evaluating BRAs. Adequate
guidance is provided in other resources for preparing a
BRA, and is referred to below and throughout the chapter.
This chapter discusses the important components of a
BRA, highlighting where up-front planning and
professional judgment are needed, and
20
For the purposes of this text, Baseline HHRA and
BRA can be used interchangeably. BRA will be used
here to avoid confusion with established EPA guidance
for HHRA (EPA, 1989i). It is understood that the
evaluation of potential environmental risks, or ERA, is
an integral part of the BRA.
The methodology presented in this chapter has largely been
developed by the EPA for activities undertaken under
CERCLA. The primary guidance documents that form the
basis for the discussion on BRA methodology are listed
below. Of these guidance documents, RAGS (USEPA,
1989j) provides the general overview and structure of the
risk assessment process. As noted earlier, a thorough
understanding of RAGS is prerequisite to the USACE
process, and redundancies will not be found in this
guidance. This guidance will, however, provide the details
necessary to focus investigations toward site closeout and
provide USACE procedures relative to performance and
evaluation of a site-specific BRA. Appendix A presents
additional selected OSWER directives and EPA regional
guidance.
&
Risk Assessment Guidance for Superfund: Human
Health Evaluation Manual (Part A) (RAGS) (USEPA,
1989j).
&
RAGS Part B (USEPA, 1991d).
&
RAGS Part C (USEPA, 1991e).
&
RAGS Part D (USEPA, 1998a).
&
Exposure Factors Handbook (USEPA, 1997c).
&
Guidance for Data Useability in Risk Assessment
(Part A) (USEPA, 1992h).
&
Guidance for Data Useability in Risk Assessment
(Part B) (USEPA, 1992k).
&
Applicable Directives from EPA's OSWER (“OSWER
Directives”) (ongoing issuance), including:
-
Guidance on Risk Characterization for Risk
Managers and Risk Assessors (USEPA, 1992d).
-
Human Health Evaluation Manual, Supplemental
Guidance: Standard Default Exposure Factors
(USEPA, 1991b).
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&
-
Supplemental Guidance to RAGS: Calculating
the Concentration Term (USEPA, 1992j).
&
Guidance for Data Useability in Risk Assessments
(Parts A and B) (USEPA, 1992h,k).
-
Revised Interim Soil Lead Guidance for
CERCLA Sites and RCRA Corrective Action
Facilities (USEPA, 1994c).
&
Laboratory Data Validation, Functional Guidelines
for Evaluating Inorganics Analyses (USEPA, 1994b).
&
Laboratory Data Validation, Functional Guidelines
for Evaluating Organics Analyses (USEPA, 1994a).
&
EM 200-1-1, Validation of Analytical Chemistry
Laboratories (USACE).
&
EM 200-1-3, Requirements for the Preparation of
Sampling and Analysis Plans (USACE).
&
EM 200-1-6, Chemical Quality Assurance for HTRW
Projects (USACE).
Various subject-specific guidance developed to
support specific aspects of risk assessment, such as:
-
Superfund Exposure Assessment Manual
(USEPA, 1988d).
-
Dermal Exposure Assessment: Principles and
Applications (USEPA, 1992c).
-
Guidelines for Exposure Assessment (USEPA,
1992i).
4.2 SUMMARY AND REVIEW OF ANALYTICAL
DATA.
The quality of a BRA is directly dependent upon the
quality of the chemical data applied. Regardless of how
well other components of the BRA are performed, if the
quality of the data is poor or the data do not accurately
reflect the site contamination or the appropriate types of
exposures, the BRA will not provide an adequate
description of potential health effects posed by the site.
Therefore, it is imperative that the types of data used in an
assessment be carefully evaluated as well as properly used.
4.2.1
Historical Data Review. In some instances,
historical data are available and can be used, in whole or
in part, with or without supplemental data, to assess
potential health risks associated with the site. Often, the
data have been collected for purposes other than for use in
a BRA and, thus, may not be appropriate for inclusion in
a BRA. Prior to inclusion in a BRA, these data must be
reviewed for useability.
4.2.2
Guidance. This chapter highlights several
factors that should be considered when evaluating data
collected specifically for a BRA, or when reviewing
existing data to determine its useability. Much of the
information presented herein has been obtained from the
following documents:
4-2
4.2.3
Evaluation of Data Quality. An evaluation of
data quality should examine five broad categories, each
discussed in the following paragraphs. The risk assessor
must be aware of the important factors within each category
to enable him or her to judge whether the data are
appropriate for inclusion in the BRA, as specified in the
DQOs. These are:
&
Data collection objectives.
&
Documentation.
&
Analytical methods/QLs.
&
Data quality indicators.
&
Data review/validation.
4.2.3.1 Data Collection Objectives. The objective of the
data collection program should be re-examined as part of
data evaluation to determine whether the type and scope of
analyses were appropriate for risk assessment purposes, and
whether supportive information (such as QA/QC protocols)
is available. Optimally, all data available for a BRA will
have been collected with consideration of specific minimum
requirements (DQOs). These data should be evaluated in
terms of the attainment of these objectives or minimum
requirements. Each factor specified as a minimum
requirement or objective should be re-examined to
determine the degree to which
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these requirements were attained during sampling and
analysis.
4.2.3.2 Documentation. The collection and analysis of
site media have been adequately documented to
demonstrate that the samples were collected, handled, and
analyzed according to the DQOs and/or minimum
requirements specified for BRA data. Documentation on
adherence to these minimum requirements should be
available for review by the risk assessor.
4.2.3.3 Analytical Methods and QLs. The analytical
methods, DLs, and QLs applied to BRA data collection
should be specified as part of the minimum requirements
prior to the data collection. Once data results are
available, the analytical methods used and DLs attained
should be re-examined to identify any deviations from the
minimum requirements, and the impact of that deviation
upon data useability.
4.2.3.4 Data Quality Indicators. Six data quality
indicators (precision, accuracy, representativeness,
completeness, comparability, and sensitivity) need to be
considered when reviewing chemical analytical results.
The assigned data evaluator/validator should examine
these factors as part of the formal data evaluation
procedures. However, it is important for the risk assessor
to understand the terms and meaning in order to
understand the data evaluation reports and how they affect
the useability of the data.
criteria for evaluating data. The risk assessor needs to be
clear about the appropriate evaluation requirements for the
protocols applied to assure appropriate interpretation of the
data.
4.2.3.6 Data Summary/Segregation of Data. General data
that have been identified as acceptable for use in a BRA
should be summarized in a manner that presents the
pertinent information to be applied in the BRA. Any
deviations from the DQOs or minimum requirements
should be identified, and the potential effects upon the BRA
described in the assessment. Any data that have been
rejected as a result of the data evaluation should be
identified, along with a reason for their rejection. At this
point in the BRA, all appropriate site data identified as
acceptable by the data evaluation process should be
combined for each medium for the purposes of selecting
COPCs for the site, as discussed in Paragraph 4.3.
However, this does not mean that all available data are to be
combined. “Appropriateness” of data should take into
consideration the area of exposure to be assessed.
4.3 SELECTION OF COPCs
4.3.1
Objectives. The objective of selecting COPCs for
the BRA is to identify a subset of chemicals detected at the
site that could pose a potential health risk to exposed
receptors. The selection process is needed for several
reasons:
&
Not all chemicals detected at a site are necessarily
related to the site. Some may be naturally occurring, a
result of anthropogenic activities or of chemical use in
offsite areas.
&
Some chemicals may be a result of inadvertent
introduction during sampling or laboratory analysis.
&
Not all chemicals detected at a site are present at
concentrations high enough to pose a potential
exposure or health threat, or may be trace elements
present at health-protective concentrations.
4.2.3.5 Data Review/Evaluation.
4.2.3.5.1
Review and evaluation of chemical data can
be performed at different levels and depths, depending on
the desired use of the data. Prior to inclusion in a BRA,
site data should undergo an evaluation process. Data
evaluation should be performed by a chemist or other
qualified individual. The risk assessor need only know
that the data have been reviewed according to acceptable
protocols, and all data have been appropriately qualified.
Summary reports from the data evaluation will inform the
risk assessor of any variations or deviations from accepted
protocols.
4.2.3.5.2
Different analytical protocols have different
data evaluation requirements. In addition, different
protocols may use different qualifiers or
The chemical selection process is performed on the data
that have been identified as useable by the data evaluation
process. COPC selection involves evaluation of these data
using a number of criteria that are designed to identify those
chemicals that are not appropriate to retain as COPCs. Through an exclusion process, the COPCs are
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selected from the list of chemicals analyzed in site media.
The outcome of the selection process is a list or lists of
chemicals in site media that are later assessed
quantitatively in the BRA.
4.3.2
General Considerations. Two general factors
should be considered before applying the chemical
selection process. These factors allow the risk assessor to
select the most appropriate data to include in the
assessment.
&
-
Not all chemical data collected from site media
represent those to which a receptor is necessarily
exposed. When selecting COPCs, the potential
receptors, exposure pathways, and exposure
routes identified in the preliminary CSM should
be examined. The preliminary CSM will identify
where exposure is expected to occur (onsite,
offsite, to surface soils, to subsurface soils,
through ground water, by direct contact, etc.).
This information is then used to help identify the
media and locations where assessments will be
directed and COPCs identified for each pathway
of concern.
A distribution analysis of the chemical presence
at the site should be conducted. This examination
would differentiate between impacted areas and
nonimpacted areas which is particularly useful at
very large sites. The distributional analysis can
be a statistical evaluation or performed
qualitatively. The distributional analysis may
identify the whole site as the exposure area or
only subunits of the site as the exposure area.
Are the chemical data appropriate?
-
4-4
4.3.3
Selection Criteria/Methodology. Criteria that
can be applied to determine whether a chemical should not
be retained as a COPC are:
&
Nondetection.
&
Comparability with background concentrations.
&
Non-site-relatedness.
&
Role as an essential nutrient and presence at healthprotective levels.
&
Limited presence.
What is the exposure area?
-
&
exposure to these locations and depths is not plausible.
Even with high quality, useable data, the form of
the chemical or sampling technique should be
examined for relevance for exposure. For
example, unfiltered ground water data may not
be relevant to exposures if all water withdrawn
from an aquifer for potable purposes is normally
filtered prior to consumption. Data composited
from multiple locations and depths may also not
be relevant to exposures if
Each criterion is discussed further in the following
paragraphs.
4.3.3.1 Nondetection. Chemicals analyzed for but not
detected in any sample of a site medium should not be
included as COPCs for that medium. Care must be taken
when evaluating analytical results in which a very high DL
was attained, since a significant concentration of a chemical
may be “masked” due to the elevated QL. Although a
quantitative estimate of the chemical's concentration value
is unavailable in such a case, the chemical may be assessed
qualitatively to determine if it is present in other site media
(if so, EPA recommends utilizing one-half of the SQL as a
proxy concentration) or re-sampling may be indicated.
4.3.3.2 Comparability with Background Concentrations.
4.3.3.2.1
Some chemicals detected in site media may be
naturally occurring or present as a result of ubiquitous or
offsite chemical use. Therefore, it is appropriate to exclude
them from the risk assessment. Background samples are
segregated from the site data, and are used exclusively to
identify non-site-related chemicals.
4.3.3.2.2
Acquisition of site-specific background
information is always preferable to regional or national
values when examining site-relatedness and comparability
to background concentrations. Literature values describing
regional or national background ranges for chemicals in
soil, ground water, surface water, and
EM 200-1-4
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sediments may be used, but only if site-specific background
information is unavailable. Regional or national ranges
are relatively insensitive and can lead to misinterpretation
of the data.
All USACE Risk Assessments Shall Include a
Statistically Robust, Significant, and Defensible
Set of Background Concentrations
Background values should be expressed as the 95%
CL on the mean. Chemicals properly applied to the
environment according to their intended use (i.e.
pesticides and herbicides) shall not be considered as
contaminants, but should be considered as a part of
the background.
In industrial areas, normal
concentrations of anthropogenic contaminants shall
be considered as part of the background.
4.3.3.2.3
Determination of comparability with
background can be accomplished in several ways,
depending on the amount of data available. Two methods
that are available are statistical evaluation and numerical
comparison.
&
&
A statistical evaluation is best utilized when a
sufficient number of site and background samples are
available to test the null hypothesis that there is no
difference between the site and background mean
chemical concentrations. This approach can be used
when the risk assessor has defined the minimum
requirements for background and site sample
numbers and sampling design. Several statistical
tests are available with which to determine whether
the two data groups, background and site, are
comparable. Texts on statistics, such as Gilbert
(1987), should be consulted for tests applicable for
use in specific site conditions. The selection of test
depends upon the distribution of the data (normal,
non-normal), whether nondetected values are
included, the number of samples, and perhaps
(depending on the test) other factors. This is the most
rigorous method of determining comparability.
Numerical comparisons can be made when the background data are more limited in number,
making a statistical comparison less meaningful. This
approach may be useful when historical data with limited
background samples are being used, or when the minimum
requirements for BRA data collection have not been met
and less than optimal numbers of background sample
results are available. The following comparisons can be
made:
-
Comparison of mean site concentration to two
(USEPA, 1995d) or three (USEPA, 1992a) times
the mean background concentration.
-
Comparison of range of detected concentrations in
both data sets.
4.3.3.5 Chemical Distribution. The physical distribution
and frequency of detection of a chemical in a site medium or
exposure area can be used to refine the list of COPCs. The
premise behind this criterion is that a chemical with a
limited presence in a medium or exposure area does not
pose as great a potential health risk as do chemicals more
frequently detected. The distribution of the chemical
presence in a site or exposure area should be examined by
identifying where the chemical was and was not detected
and its frequency of detection. If this evaluation indicates
that the distribution of the chemical is low, i.e., it is detected
in only one or a few locations, it may be reasonable to
exclude it as a COPC, or to select the chemical as a COPC
for a smaller exposure area of the site. This screening
should be performed in conjunction with the toxicity
screening to assure that chemicals representing risks to
receptors are not eliminated unnecessarily from the list of
COPCs.
4.3.4
Presentation of COPCs. The conclusion of the
chemical selection process is a subgroup of chemicals that
are selected as COPCs and which will be used in the BRA.
Tables should be developed segregating the COPCs
selected for each medium and/or exposure area. All
chemicals that were removed from consideration should be
identified, with an explanation of the reason for their
exclusion.
4.4 EXPOSURE ASSESSMENT
The purpose of the exposure assessment of a BRA is to
estimate the nature, extent, and magnitude of potential
exposure (or site-specific dose) of receptors to COPCs that
are present at or migrating from a site, considering
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both current and plausible future use of the site. Several
components of the exposure assessment have previously
been characterized during earlier stages of the site
investigation for the purposes of developing the CSM and
focusing investigative activities. These components
include identification of potential receptors, exposure
pathways, and exposure areas. These preliminary
characterizations were based upon early and often
incomplete information that now must be clarified in light
of the information obtained during the RI.
4.4.1
Refinement of the CSM. The CSM is a
representation of certain aspects of the exposure
assessment. Its earlier formulation was based upon
assumptions regarding chemical presence and migration,
which now should be verified and revised (if necessary)
with information collected during the site investigation.
4.4.2
Characterization of the Exposure Setting.
4.4.2.1 The objective in describing the exposure setting
is to identify the site physical features that may influence
exposure for both current and future scenarios. While
each site will differ in the factors that require
consideration, some of the more common factors are listed
below and discussed briefly. Examples of how the factor
may influence exposures are also provided.
&
&
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4-6
Geology. The land type and forms may influence
exposure in various ways. For example, the
topography of the area can influence the direction of
chemical migration to offsite areas. The presence of
surface water bodies may indicate potential exposures
through recreational or potable use of the water or
through the consumption of aquatic organisms (i.e.,
fish and shellfish).
Hydrogeology.
The number, types, and
characteristics of aquifers (depth, salinity, use, ground
water flow direction, and velocity) should be
examined to evaluate whether exposure to ground
water is possible and, if so, where, when, and to
whom.
Climate. The temperature and precipitation profile of
the area may limit the frequency of exposure (e.g.,
frozen surface water bodies, extent of outdoor
activities) as well as influence the extent of
chemical migration (e.g., rates of volatilization and
infiltration).
&
Meteorology. Wind speed and direction may influence
the entrainment of soil particles and the extent of transport and dilution of air contaminants.
&
Vegetation. The extent of vegetation may influence the
availability of soil for dermal, ingestion, or inhalation
exposure and the potential for exposure through the
food chain.
&
Soil type. The type of soil (e.g., grain size, organic
carbon, clay content) may influence soil entrainment,
the degree of chemical binding, and leaching potential.
4.4.2.2 Description of the site setting in the exposure
assessment should involve obtaining more specific, in-depth
information than obtained during the preliminary CSM
development and should be supplemented by data collected
during the RI. Descriptions of portions of the exposure
setting may have been discussed in other portions of the site
report, and need only be referenced in this portion.
However, characteristics of the exposure setting that are
specific to potential exposures should be presented.
4.4.3
Identification of Exposure Pathways and
Intake Routes.
4.4.3.1 An exposure pathway is the physical course a
chemical takes from the source to the receptor exposed.
Chemical intake is how a chemical enters a receptor after
contact, e.g., by ingestion, inhalation, or dermal absorption
(USEPA, 1992i). These two components are considered
together in this paragraph to identify potential exposures.
A complete exposure pathway consists of the following
elements:
&
A source and mechanism of chemical release.
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An intermedia transport mechanism (if the exposure
point differs from the source).
&
Migration pathway.
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A receptor group who may come into contact with site
wastes.
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An exposure route through which chemical uptake by
the receptor occurs.
As the field investigation has been accomplished, the
chemical data can now be evaluated to determine the
completeness of the pathways identified in the CSM.
4.4.3.2 Potential Exposure Routes. When performing
the exposure assessment, the following exposure routes
should be examined regarding the completeness of the
pathway.
&
Ingestion of water.
&
Dermal contact with water.
&
Ingestion of soil or sediments.
&
Dermal contact with soil or sediments.
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Inhalation of both vapor phase chemicals and
particulates.
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Exposure to biota (i.e., Ingestion of plant or animal
species).
4.4.4
Identification
of Potential Receptor
Populations. The identification of potentially exposed
receptor populations (completed during the TPP process)
involves defining the current and anticipated future use of
the site, and identifying the current and future activities of
receptors on or near the site. At this point in the
assessment, it is necessary to revisit those assumptions and
evaluate whether any modifications in the preliminary
assumptions are required. Chemical and physical data
collected either onsite or offsite may indicate that certain
receptor groups are not at risk, or that new receptors may
need to be evaluated.
Future Land Uses for Risk Assessment Purposes
and for Development of RAOs Shall be Land Uses
that are Reasonably Expected to Occur at the Site
or Facility
Property that is currently used for industrial or
commercial purposes at facilities will most likely be
used for those same purposes in the future. Even in
closure situations, the land use frequently stays the
same. Residential land use should not be the default
land use unless it is reasonably expected to occur. It
is very important the future land use be discussed
early with regulators, city/county zoning officials,
and the public.
4.4.5
Quantitation of Exposure (Intake or Dose).
Chemical intakes, or doses, are estimated for exposures that
could occur from complete exposure pathways for each
receptor group. The exposures are quantified with respect
to the magnitude, frequency, and duration of exposure to
derive an estimate of chemical intake or site-specific dose.
Intakes of chemicals are estimated by combining two
general components:
the chemical concentration
component (or exposure point concentration) and the intake/exposure factors component. Estimation of the
exposure point concentration, selection of intake and
exposure factors, and specific methods of combining them
mathematically are presented below.
4.4.5.1 Estimation of Exposure Point Concentrations.
Exposure point concentrations represent the chemical
concentrations in environmental media that the receptor will
potentially contact during the exposure period. They may
be derived from either data obtained from sampling or from
a combination of sample data and fate and transport
modeling, both of which are described below.
4.4.5.1.1
For current (and perhaps some future)
exposure scenarios where the current site data are
anticipated to be reasonably reflective of exposure point
concentrations over the exposure period, the exposure point
concentration can be directly derived from site data. For
future (and perhaps some current) exposure scenarios,
where current site conditions are not anticipated to be
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representative of exposure point concentrations over the
exposure period, some form of fate and transport modeling
or degradation calculations should be applied to derive
these concentrations. The available data need to be
examined critically to select the most appropriate data to
describe potential exposure.
4.4.5.1.2
Many fate and transport models are available
with which to predict exposure point concentrations from
existing site data. These models are presented in other
references and include the following:
&
Superfund Exposure Assessment Manual (USEPA,
1988d).
&
Air/Superfund National Technical Guidance Study
Series (Volumes I - V) (USEPA, 1989a, 1990e,
1992o, 1993c, and 1995b).
&
A Workbook of Screening Techniques for Assessing
Impacts of Toxic Air Pollutants (USEPA, 1988h).
&
Selection Criteria for Mathematical Models Used in
Exposure Assessments: Ground-water Models
(USEPA, 1988e).
&
Selection Criteria for Mathematical Models Used in
Exposure Assessments: Surface Water Models
(USEPA, 1987a).
&
Rapid Assessment of Exposure to Particulate
Emissions from Surface Contamination Sites
(USEPA, 1985).
&
Methodology for Assessing Health Risks Associated
with Indirect Exposure to Combustor Emissions
(USEPA, 1990b).
4.4.5.1.3
The type of model and level of effort
expended in estimating exposure point concentrations with
a model should be commensurate with the type, amount,
and quality of data available. In general, it is best to begin
with a model that employs simplified assumptions (i.e., a
“screening level” approach) and determine whether
unacceptable health risks are posed by the exposure point
concentration estimated by this approach. If so, a more
complex model that applies less conservative assumptions
should be used to then derive the exposure point
concentrations.
4-8
A Minimum of Two Risk Estimates Should be
Presented for Each Land Use Scenario: the RME
and the CT.
The goal of the BRA is to provide information on
potential risks presented by contamination for risk
managers to make informed decisions regarding future
action. The risk manager needs more information than
just worst case to make a good risk management
decision. Multiple exposure scenarios within a land
use paradigm should be used in the risk assessment to
provide the risk manager with information relative to
ranges of the perceived risks.
In order to describe a range of potential exposures
presented by a site, the BRA should assess more than one
potential exposure scenario. Use of a single expression of
potential health risks does not provide information on the
possible range of health risks, and does not allow the risk
manager to evaluate the “reasonableness” of the estimate.
Current risk assessment guidance suggests assessing an
exposure scenario that represents the high end of the risk
distribution, relating to a 90th percentile exposure (often
referred to as an RME scenario), and a scenario which more
closely describes an average exposure (or CT) (USEPA, 1992d). Presentation of both (and perhaps additional)
scenarios provides information about the range of potential
risks.
4.4.5.1.4
Numerous sources are available to select
appropriate intake and exposure factors for use in a BRA
(see Section 4.1 for the primary EPA guidance documents).
In addition to these general references, some EPA regional
offices and state environmental or health agencies have
developed exposure risk assessment guidance to
supplement the EPA Federal guidance.
4.4.5.1.5
Some of the EPA documents provide ranges
of values for intake and exposure factors, while others
present values intended to represent a specific exposure.
For example, the Standard Default Exposure Factors
(USEPA, 1991b) was developed as guidance only, and the
values are intended to be used when site-specific
information is not available. EPA encourages the use of
site-specific data so that risks can be evaluated to more
closely reflect site-specific exposures. Default values
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should be used to calculate a high end exposure only when
there is a lack of site-specific data or alternate values
cannot be justifiably supported.
The Exposure Assessment of a BRA Shall Utilize
Site-Specific Frequencies and Durations
Whenever Possible.
Where possible, the BRA should use site-specific
parameters for input into the risk algorithms. By
the use of these parameters, the BRA will tailored to
the actual expected exposures.
Additionally,
anticipated ranges of values may be used when the
BRA utilizes probabilistic methods.
4.4.5.1.6
All values that are used in estimating
chemical intake should be clearly presented in the
assessment, the source of the value should be identified,
and the rationale for using the value provided.
absorbed for a number of reasons, including the chemical
form, competition with other factors (e.g., food in the
stomach), damage of the organ (e.g., stomach, lung), effect
of the medium in which the chemical is contained, and
others. Many of these cannot be reliably addressed in a
BRA; however, two of these can, the chemical form and the
effect of the medium on absorption.
4.4.5.2.4
The form of the chemical can affect the degree
of absorption into the body. This factor is most important
for chemicals that form compounds (such as metals and
cyanide) and chemicals that exist in different valence states
(again, some metals). For example, soluble compounds of
metals such as barium sulfate are readily absorbed through
the stomach, whereas insoluble forms such as barium
carbonate are usually not absorbed. Usually, when
environmental media are analyzed, chemicals are reported
as an isolated entity (e.g., barium), and no information is
provided on valence state or compounds that existed in the
medium. However, if the form of the chemical used at the
site is known, and information on the absorption of that
chemical form is available, the intake equation can be
modified to account for a specific absorption.
4.4.5.2 Calculation Methodology.
4.4.5.2.1
RAGS identifies general intake equations for
each exposure pathway and should be consulted when
performing the intake assessment.
Some overall
assumptions in the use of these equations are presented in
the following paragraphs.
4.4.5.2.2
The intake equations developed by EPA for
the ingestion and inhalation pathways do not contain a
factor to account for bioavailability and, therefore, may
predict an intake higher than one that would occur in
actual circumstances. By not including a factor to consider
bioavailability, it is assumed that 100 percent of the
chemical detected in the medium is bioavailable.
Modifications may sometimes be made to these intake
equations to account for this factor, if the appropriate
information is available.
4.4.5.2.3
Bioavailability refers to the ability of a
chemical to be “available” in the body to interact and have
an effect. There are many aspects to bioavailability;
however, the type most of concern to BRAs is the ability
of the chemical to be absorbed into the body. Although the
medium in which the chemical is contained may be
contacted, the chemical may not be
4.4.5.2.5
The medium in which the chemical is
contained also can affect the degree of bioavailability. This
is most pronounced in media that demonstrate an ability to
bind chemicals (such as soil and sediments). When
ingested or inhaled into the body, a competition occurs
between retention of the chemical on the medium and
absorption of the chemical into the body. Therefore, some
of the chemical may be excreted from the body without
having been absorbed and some may have been absorbed
and available to exert an effect. Many factors can influence
the degree to which the medium will bind the chemical,
most of which cannot be reliably predicted (for example,
nature of the medium [organic carbon or clay content,
particle size], other chemicals being absorbed, pH, organ
condition, etc.). In some instances, information may be
available on the degree to which a particular medium affects
specific absorption routes, and the equation can be modified
to account for these influences.
4.4.5.2.6
In most assessments, it is assumed that the
chemical concentrations remain constant over time, often
for as long as 30 years. In many cases, this assumption will
not be valid. Chemical concentrations are usually
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reduced over time by degradation, migration, dilution,
volatilization, or other removal processes. If the
appropriate site-specific characteristics for natural
attenuation (e.g., soil properties, climate, pH, grain size,
etc.) are known and can be quantified, a concentration that
decreases over time can be derived for assessing intakes
through modeling.
4.4.5.3 Assessment of Uncertainties. At the conclusion
of the exposure assessment, the uncertainties associated
with the estimation of chemical intake should be
summarized. The basis for the uncertainty should be
identified (e.g., use of a default parameter), the degree of
the uncertainty qualitatively estimated (low, medium or
high), and the impact of the uncertainty stated
(overestimate and/or underestimate).
4.5 TOXICITY ASSESSMENT
4.5.1
Objectives. The toxicity assessment fulfills two
objectives in a risk assessment. First, it results in the
selection of appropriate toxicity values to use in generating
estimates of potential health risks associated with chemical
exposure. This is accomplished by identifying appropriate
sources of toxicity values and reviewing the available
information to identify the most appropriate values to use.
Second, the toxicity assessment forms the basis for
developing summaries of the potential toxicity of the
COPCs for inclusion in the risk assessment. This is
accomplished by reviewing the available information on
the toxicity of the COPCs and summarizing the factors
pertinent to the exposures being assessed.
4.5.2
Derivation of Toxicity Values. Most toxicity
values applied to risk assessments have been developed by
EPA and generally do not need to be developed by the risk
assessor. However, to appropriately select and use toxicity
values, and to identify assumptions and uncertainties
associated with them, an understanding of the development
is needed. For a complete discussion of this procedure,
see RAGS (USEPA, 1989j).
4.5.3
and are expressed in terms of (mg/kg-dy)-1. EPA's Human
Health Assessment Group reviews the SFs developed by
different EPA program offices to reach an agency consensus
on the value and to verify the SF.
4.5.3.2 In addition to the numerical value, each potentially
carcinogenic chemical is assigned a “weight of evidence”
category, expressing the likelihood that the chemical is a
human carcinogen. Six categories exist (A, B1, B2, C, D,
and E). In general, carcinogenic assessments are performed
for chemicals in groups A, B1, B2, and on a case-by-case
basis in group C.
4.5.4
Toxicity Assessment For Noncarcinogenic
Effects.
4.5.4.1 Chemicals that cause toxic effects other than
cancer such as organ damage, physiological alterations, and
reproductive effects are generically grouped as
noncarcinogens. These types of toxicants share one point
in common in regard to their effects: the apparent
occurrence of a toxicological threshold. This threshold is an
exposure level that must be exceeded for the adverse impact
of the chemical to manifest itself. Below this threshold,
factors such as the body's protective mechanisms (e.g.,
metabolism, elimination) can limit the chemical effects,
preventing the expression of adverse effects. The basis of
the derivation of noncarcinogenic toxicity values, then, is to
identify this threshold level, and modify it to express
potential human toxicity.
4.5.4.2 The toxicity descriptor most commonly used in
risk assessments for describing a chemical's
noncarcinogenic toxicity is the reference dose (RfD) or
reference concentration (RfC). An RfD or RfC “is a
provisional estimate (with uncertainty spanning perhaps
several orders of magnitude) of a daily exposure to the
human population (including sensitive subgroups) that is
likely to be without an appreciable risk of deleterious effects
during a portion of a lifetime, in the case of a subchronic
RfD or RfC, or during a lifetime, in the case of an RfD or
RfC” (USEPA, 1992e).
Toxicity Assessment for Carcinogenic Effects.
4.5.4.3 Several types of RfDs are available:
4.5.3.1 The toxicity value used to describe a chemical's
carcinogenicity is the cancer slope factor (SF). Two types
of SFs are available: oral SFs and inhalation SFs,
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Chronic RfDs, used to assess chronic exposures
(greater than 7 years [one-tenth of a lifetime]). Two
different types of chronic RfDs are available: oral
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chemical and physical properties, synonyms, and
other information.
RfDo and inhalation RfD i. More recently, RfCs
have been developed for the inhalation route.
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Subchronic RfDs, for exposures between 2 weeks and
7 years. Both oral and inhalation subchronic RfDs
(RfDso and RfDsi, respectively) may be available.
&
Developmental RfDdt, used to evaluate potential
effects on a developing organism following a single
exposure event (very few have been developed).
4.5.4.4 EPA's RfD workgroup reviews and verifies
existing chronic RfDs and develops new RfDs, and
resolves conflicting toxicity values developed within the
EPA in the past. The RfD workgroup also states the
degree of confidence associated with the study, the
database, and the RfD (low, medium, or high).
Subchronic RfDs are not reviewed or verified and are,
therefore, considered unverified values. These values
should only be used when chronic RfDs are not available.
4.5.5
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Health Effects Assessment Summary Tables (HEAST).
This document is published annually by EPA and is a
collection of interim and provisional toxicity values
developed by EPA. Verified toxicity values are not
presented in the most current version of HEAST,
rather, the user is directed to IRIS. HEAST can be
obtained through the National Technical Information
Service (NTIS).
&
EPA's Superfund Health Risk Technical Support
Center (513-569-7300). Assistance may be requested
from these offices on the existence of provisional
toxicity values not presented in either IRIS or HEAST
or on other factors relating to risk assessment.
However, EPA only provides services for sites being
managed under the Federal Superfund Program.
&
For sites other than Superfund, the USACE user is
directed to contact the appropriate DOD Toxicology
and Research Program offices:
USACHPPM
Toxicology Directorate at:
http://chppm-www.apgea.army.mil/tox/program.htm,
then contact the Health Effects Research Program
Manager; or contact the Air Force Research
Laboratory, Human Effectiveness Directorate,
Operational Toxicology Division at:
http://voyager.wpafb.af.mil or (937) 255-5150 x3105.
Sources of Toxicity Values.
4.5.5.1 Several sources of up-to-date toxicity values and
supplementary information are available. These sources
are presented below. A hierarchical approach is
recommended when consulting these sources:
if
information is not available through the first source, the
second should be consulted, and so forth.
&
Integrated Risk Information System (IRIS). This is
EPA's primary database for the reporting of up-todate toxicity values that have been verified by the
EPA. IRIS may be accessed through the Internet at
http://www.epa.gov/ngispgm3/iris/index.html. IRIS
contains chemical profiles that present verified
chronic RfDs, chronic RfCs, and cancer SFs. The
study(s) from which the toxicity value was derived is
summarized, and the method of derivation is
explained (e.g., applied uncertainty and modifying
factors, level of confidence, extrapolation model).
Supplementary toxicity information is also sometimes
included. In addition, some IRIS files contain
regulatory information (such as the SDWA Maximum
Contaminant Levels [MCLs] and CWA Ambient
Water Quality Criteria), and often
4.5.5.2 Additional information on the toxicity of the
chemicals can be found in the following general sources:
&
EPA criteria documents such as those regarding
drinking water, ambient water, and air quality, as well
as health effects assessment documents.
&
Toxicological Profiles developed by ATSDR.
4.5.6
Use of Toxicity Values. Toxicity values
developed by EPA can generally be used directly in a risk
assessment with few or no modifications. The mechanism
for combining toxicity values with exposure or intake
estimates is described in Section 4.7. However, there are a
number of factors that should be considered
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when applying these toxicity values. These are discussed
in the following paragraphs.
&
Military unique chemicals.
4.5.7.1 Toxicity Values for Lead.
4.5.6.1 Absorption Considerations. Most toxicity values
are based on administered, rather than absorbed, doses,
and the absorption efficiency has not been considered.
However, whatever absorption has occurred during the
toxicological study is usually inherent in the toxicity value.
Therefore, use of a toxicity value assumes that the extent
of absorption observed in the study is also appropriate for
the exposure pathway being assessed. Differences in
absorption efficiencies between that applicable to the
toxicity value and that being assessed may occur for a
number of reasons. Two factors that will influence
absorption efficiencies are differences in chemical form
and differences in the exposure medium.
4.5.6.2 Use of Oral Toxicity Values for Assessment of
Dermal Exposure Route. EPA does not generate toxicity
values for dermal exposures. As a surrogate, oral toxicity
values are applied to the assessment of dermal exposures.
However, since dermal intakes are based upon absorbed
doses and most oral toxicity values are based upon
administered doses, the oral toxicity value may be
modified before using in a dermal assessment. For a
complete discussion of this procedure, when it should be
used, and the appropriate procedures for its application,
see Appendix A of RAGS (USEPA, 1989j).
4.5.7
Special Chemicals. Some chemicals commonly
detected at a site require a specific methodology to
generate a toxicity value or are reported in a manner that
influences the toxicity value. The following chemicals are
discussed relative to these special circumstances:
&
Lead.
&
PAHs.
&
Polychlorinated biphenyls (PCBs).
&
Chlorinated dibenzo-p-dioxins and dibenzofurans
(CDDs/CDFs).
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Total petroleum hydrocarbons (TPH) and other
petroleum groupings.
4.5.7.1.1
Lead is a unique chemical in its
pharmacokinetic and toxicological properties. Although
classified as both a potential carcinogen (B2 weight of
evidence) and a noncarcinogen, lead is most often assessed
as a noncarcinogen only, since these effects manifest
themselves at doses lower than those for carcinogenicity.
However, in contrast to the assumption of the existence of
a threshold for noncarcinogenic responses, there does not
appear to be a threshold below which lead does not elicit a
response. For these reasons and others (including lead's
propensity to accumulate in bone tissue), the use of blood
lead (PbB) levels, rather than chronic daily intakes, is the
best indicator of potential adverse impacts). EPA has not
developed a noncarcinogenic RfD or a carcinogenic SF for
lead.
4.5.7.1.2
EPA has developed an exposure model for
lead that considers both its biokinetics and toxicological
properties. The IEUBK model (Pub. #9285.7-15-2, PB93963511) is available through NTIS. The model integrates
the intake of lead from multiple sources, including soil,
food, and water ingestion, inhalation, and, when
appropriate, maternal contributions. Intakes are assessed
for children from the ages 0 (birth) to 7. The model does
not assess lead intakes for older children or adults.
Childhood exposure to lead is the focus of this assessment
because this receptor group is recognized as the most
sensitive to the noncarcinogenic effects of lead.
Use of the EPA’S IEUBK Model for Lead
Exposures Should be Limited to Residential,
Childhood Exposures Only.
Where adult and/or non-residential exposures are
expected, a more appropriate model should be used.
See Recommendations of the Technical Review
Workgroup for Lead for an Interim Approach to
Assessing Risks Associated with Adult Exposures to
Lead in Soil (USEPA, 1996c).
4.5.7.1.3
The IEUBK model integrates intakes of lead
from multiple exposure routes and predicts a PbB level,
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in µ g/dL, at different ages (up to 7 years of age). The
maximum predicted PbB level can then be compared with
a threshold level of 10 µg/dL, which EPA has adopted as
an “acceptable” PbB level.
4.5.7.1.4
Use of the IEUBK model is recommended
when children of this age group are anticipated to be
receptors at a site. However, when adults are the only
potential receptors, the EPA’s Technical Review
Workgroup for Lead has developed an interim approach
for evaluating adult soil lead exposure. Recommendations
of the Technical Review Workgroup for Lead for an
Interim Approach to Assessing Risks Associated with
Adult Exposures to Lead in Soil (USEPA, 1996c)
provides the currently accepted methodology. This interim
guidance is available on the Internet at:
http://www.epa.gov/superfund/oerr/ini_pro/lead.
4.5.7.2 Toxicity Values for PAHs.
4.5.7.2.1
PAHs, also known as polynuclear aromatic
hydrocarbons or polynuclear aromatics, are a class of compounds containing hydrogen and carbon in multiple ring
structures. There are numerous possible PAH molecules,
many of which are commonly analyzed for in a
semivolatile chemical analysis.
4.5.7.2.2
PAHs are a natural component of petroleum
and are found in heavier petroleum fractions such as lube
oil, naphtha, jet fuel, etc. PAHs are also produced by the
incomplete combustion of organic matter, and are created
during fires, volcanoes, combustion of gasoline, burning of
wood, etc. For these reasons, PAHs are ubiquitous in the
environment at low levels, particularly in soil and
sediments, to which they readily bind.
4.5.7.2.3
Some PAHs are classified by EPA as
potential human carcinogens, including:
&
Benzo(a)anthracene.
&
Benzo(a)pyrene.
&
Benzo(b)fluoranthene.
&
Benzo(k)fluoranthene.
&
Chrysene.
&
Dibenzo(a,h)anthracene.
&
Indeno(1,2,3-cd)pyrene.
4.5.7.2.4
EPA has developed a cancer SF for one
carcinogenic PAH only: benzo(a)pyrene. However,
comparative toxicity values have been proposed for the
other carcinogenic PAHs that describe the toxicity relative
to the toxicity of benzo(a)pyrene. Several sets of comparative toxicity values have been proposed. The EPA’s
Provisional Guidance for Quantitative Risk Assessment of
Polycyclic Aromatic Hydrocarbons (USEPA, 1993b)
should be consulted for Toxicity Equivalence Factors
(TEFs) to utilize in this assessment.
4.5.7.2.5
Other PAHs are considered by EPA to be
noncarcinogens; however, only a few of these currently have
RfDs. Currently, there is no comparative toxicity approach
for estimating the toxicity of noncarcinogenic PAHs that do
not have RfDs.
4.5.7.3 Toxicity Values for PCBs.
4.5.7.3.1
PCBs are a group of chlorinated compounds
based on the biphenyl molecule. There are 209 possible
individual congeners of PCBs, differing in the degree and
location of chlorination. PCBs are seldom analyzed as
individual compounds; rather, they are commonly analyzed
as total PCBs, Aroclor compounds (a commercial mixture,
with AroclorTM being Monsanto's trade name) or sometimes
in congener groups (such as tetrachlorobiphenyls or
pentachlorobiphenyls). When analyzed as Aroclors, the
results are expressed relative to different commercial
mixtures of Aroclor, such as Aroclor 1248, Aroclor 1254,
or Aroclor 1260.
4.5.7.3.2
The toxicity values (cancer SF and RfD)
developed for PCBs are based on specific Aroclor mixtures
-- the SF is based on Aroclor 1260 and the RfD of Aroclor
1016. These values are used to assess the potential impacts
of PCBs reported in any form (i.e., another Aroclor mixture
or total PCBs). However, it is known that the toxicity of
PCBs varies between these congeners. Most notably, the
carcinogenic potency is less in smaller molecular weight
chlorinated biphenyls. Therefore, application of the Aroclor
1260 cancer SF to
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Aroclor 1232 or 1248 mixtures may overestimate the
degree of health risk posed by the PCB.
4.5.7.3.3
EPA recommends the use of a tiered
approach to the evaluation of PCB carcinogenicity, even
though toxicity values for the different Aroclors are still
available. Information on the application of this procedure
can be found on the IRIS database, accessible on the
Internet at:
http://www.epa.gov/ngispgm3/iris/index.html.
4.5.7.4.4
A toxicity value (cancer SF) is available for
2,3,7,8-TCDD. As a policy, EPA has developed a TEF
approach for other CDDs/CDFs, wherein the toxicities of
these other compounds are expressed relative to the toxicity
of 2,3,7,8-TCDD. These values can be used to express the
amount of CDDs/CDFs present in a sample as “2,3,7,8TCDD equivalents.” Further discussion of the TEFs for
CDDs/CDFs can be found in USEPA, 1989d.
4.5.7.5 Toxicity Values for TPHs and Other Petroleum
Groupings.
4.5.7.4 Toxicity Values for CDDs/CDFs.
4.5.7.4.1
CDDs/CDFs, often abbreviated “dioxins and
furans,” are a group of chlorinated compounds based on
the dibenzo-p-dioxin or dibenzofuran molecule (both of
which are structurally similar). CDDs/CDFs are not
compounds used for commercial purposes in the past, and,
outside of research, have no known use. Rather,
CDDs/CDFs are byproducts of high temperature
combustion of chlorinated compounds and impurities in
other chemical products such as pentachlorophenol or
PCBs. Although not considered a “natural” product, some
forms of CDDs and CDFs (specifically octa-CDD and
octa-CDF) are ubiquitous in the environment at very low
concentrations.
4.5.7.4.2
There are 75 possible CDD congeners and
135 possible CDF congeners. As with PCBs, the degree
of toxicity varies with the degree and location of the
chlorine atoms on the hydrocarbon ring, becoming higher
when the 2, 3, 7, and 8 positions of the molecule have
chlorine atoms. Considered the most potent CDD,
2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is
the reference against which all other CDDs and CDFs are
compared.
4.5.7.4.3
Analysis of CDDs and CDFs is most
commonly reported by congener group (i.e., as either
tri-, tetra-, penta-, hexa-, hepta-, or octachlorodibenzo-pdioxin or -dibenzofuran). Within these groups the results
are often further separated into “2,3,7,8- substituted” or
“other” categories. This form of reporting is needed to
appropriately assess CDDs and CDFs. Reporting as “total
dioxins” or even just by congener group may require the
assumption that all CDDs/CDFs present are as toxic as
2,3,7,8-TCDD, resulting in an overestimate of potential
health risks posed by the presence of CDDs/CDFs.
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4.5.7.5.1
Use of chemical-specific data to derive an
estimate of potential health risks is the recommended
method of performing a BRA. Use of chemical groupings
such as TPH is less than optimal, since these types of
chemical groupings vary in their chemical composition and,
hence, toxicity.
4.5.7.5.2
Some attempts have been made to derive
toxicity values for TPH. However, since the composition of
TPH varies from place to place (even within the same site)
with the age of the spill, and the type of fuel spilled or
disposed, it is unlikely that these estimates are valuable
descriptors of the potential toxicity of the components
comprising the TPH detection.
4.5.7.5.3
For some other chemical groupings, toxicity
tests have been performed on the specific mixture, and adequately describe the toxicity of the chemical grouping,
such as jet fuel and diesel fuel. One potential pitfall to using
these values is that the RfD may represent the toxicity of the
mixture when fresh, but may not represent the toxicity of the
mixture after release to the environment. When released,
processes such as biodegradation, chemical migration, and
transport may alter the composition of the mixture, making
it more concentrated in some compounds and less
concentrated in others. In these instances as well, chemicalspecific analysis of the media is preferred.
4.5.7.6 Toxicity values for Military Unique Chemicals.
Many DOD sites contain potentially toxic chemicals not
commonly found except on military sites. Military unique
chemicals may include explosives, rocket fuels, radioactive
materials, chemical agents, or degradation products of these
compounds. Because of the unique status of many military
compounds, EPA is often unable to supply toxicity
information. Toxicity information can
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usually be obtained by contacting the USACHPPM
Toxicology Directorate at:
http://chppm-www.apgea.army.mil/tox/program.htm, then
contact the Health Effects Research Program Manager.
level of intake that is recognized as unlikely to result in
adverse noncarcinogenic health effects (i.e., the RfD). The
comparison of estimated intake and acceptable exposure
level is called a hazard quotient (HQ).
4.6 RISK CHARACTERIZATION
4.6.2.2.2
An HQ of 1 indicates that the estimated intake
is the same as the RfD, whereas an HQ greater than 1
indicates the estimated intake exceeds the RfD. No further
conclusions can be drawn as the relationship between intake
and toxicity used to derive the RfD is not linear. In contrast
to cancer risk estimates, HQs can range from values less
than 1 to greater than 1.
4.6.1
Objective. In the risk characterization, the
chemical intakes estimated in the exposure assessment are
combined with the appropriate critical toxicity values
identified in the toxicity assessment. The results are the
estimated cancer risks and noncarcinogenic health hazards
posed by the exposures. Along with the numerical
estimates of potential health risks and hazards, a narrative
describing the primary contributors to health risks and
hazards and factors qualifying the results are presented.
4.6.2
Methodology. In the following paragraphs, the
methodology is presented for performing the quantitative
risk characterization for carcinogens, followed by the
methodology for noncarcinogens. These are discussed
separately because different methodologies are used for
each of these classes of chemicals.
4.6.2.1 Carcinogenic Risks. The objective of a risk
characterization for carcinogenic chemicals is to derive an
estimate of the overall cancer risk associated with
exposure to all potential carcinogens at a site through all
routes of exposure for a given receptor group, for both CT
and RME current and future use scenarios. To derive this
value, the cancer risk associated with exposure to a single
carcinogen through a single exposure pathway is estimated. These single chemical risk estimates are then
combined (added) within a pathway to describe the risk
associated with a given pathway. Pathway-specific risks
are then combined (added) for all exposure pathways for
a given receptor group to derive an overall risk estimate
for each of the cases.
4.6.2.2 Noncarcinogenic Hazards.
4.6.2.2.1
The objective of a risk characterization for
noncarcinogenic chemicals is to compare the estimated
chemical intake of one chemical through one exposure
route with the “threshold” concentration; that is, the
4.6.2.2.3
To examine the potential for the occurrence
of adverse noncarcinogenic health effects as a result of
exposure to multiple noncarcinogens through multiple
exposure pathways (for each of the exposure scenarios;
current-future for average and upper bound exposures), it
is assumed that an adverse health effect could occur if the
sum of the HQs exceeds 1. In other words, even if exposure
to each individual chemical is below its RfD (HQ less than
1), if the sum of the ratios for multiple chemicals exceeds
unity, adverse health effects could occur.
4.6.2.2.4
Applying the assumption of additivity is
considered to be a conservative approach, but may
overestimate or underestimate the actual potential health
risk presented by the exposure. If the overall hazard index
(HI) is greater than unity, consideration should be given to
the known types of noncarcinogenic health effects posed by
exposure to the chemicals. If the assumption of additivity
is not valid (i.e., if the chemicals most strongly contributing
to the exceedance of the HI display very different types of
noncarcinogenic effects) the HI may be segregated
according to toxicological endpoint. These segregated HIs
may then be examined independently.
4.6.2.2.5
Factors that need to be considered in
segregation of endpoints include the critical toxicological
effect upon which the toxicity value is based, as well as
other toxicological effects posed by the chemical at doses
higher than the critical effect. Major categories of toxic
effects include neurotoxicity, developmental toxicity,
immunotoxicity, reproductive toxicity, and individual target
organ effects (hepatic, renal, respiratory, cardiovascular,
gastrointestinal, hematological, musculoskeletal, dermal,
and ocular) (USEPA, 1989j).
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4.7 EVALUATION OF UNCERTAINTIES AND
LIMITATIONS
4.7.1
Objective.
4.7.1.1 EPA has identified two requirements for full
characterization of risk. First, the characterization must
address qualitative and quantitative features of the
assessment. Second, it must identify any important
uncertainties in the assessment. Methods of identifying
and describing uncertainties in a risk assessment are
discussed below.
4.7.2
Sources of Uncertainty. Sources of uncertainty
exist in almost every component of the risk assessment.
Overall, uncertainties can arise from two main sources:
variability and data gaps. Uncertainty from variability can
enter a risk assessment through random or systematic error
in measurements and inherent variability in the extent of
exposure of receptors. Uncertainty from data gaps is most
prominently seen when approximations are made regarding
exposures, chemical fate and transport, intakes, and toxicity.
Specific sources of uncertainty in a risk assessment are
identified and discussed below. Following this discussion,
different approaches for conducting an uncertainty
evaluation are presented.
4.7.1.2 According to recent guidance (USEPA, 1992d):
“EPA risk assessors and managers need to be
completely candid about confidence and uncertainties
in describing risks and in explaining regulatory
decisions. Specifically, the Agency's risk assessment
guidelines call for full and open discussion of
uncertainties in the body of each EPA risk
assessment, including prominent display of critical
uncertainties in the risk characterization. Numerical
risk estimates should always be accompanied by
descriptive information carefully selected to assure an
objective and balanced characterization of risk in risk
assessment reports and regulatory documents.”
4.7.2.1 Uncertainties Associated with Sampling and
Analysis.
4.7.2.1.1
The identification of the types and numbers of
environmental samples, sampling procedures, and sample
analysis all contain components that contribute to
uncertainties in the risk assessment. Decisions regarding
the scope of sampling and analysis are often made based on
the CSM developed at the planning stages of the
investigation. While appropriate planning may minimize
the uncertainty associated with these components, some
uncertainty will always exist, and cannot always be reduced
realistically, rather it may be sufficient to just understand the
degree of uncertainty associated with the assessment.
4.7.1.3 Identification and discussion of uncertainty in an
assessment is important for several reasons (USEPA,
1991a):
4.7.2.1.2
Some of the assumptions in this component
that contribute to uncertainty in the assessment include:
&
Information from different sources carries different
kinds of uncertainty, and knowledge of these
differences is important when uncertainties are
combined for characterizing risk.
&
&
Decisions must be made on expending resources to
acquire additional information to reduce uncertainties.
&
A clear and explicit statement of the implications and
limitations of a risk assessment requires a clear and
explicit statement of related uncertainties.
Media sampled. Due to budget limitations, only
representative areas of the site are selected for
sampling and analysis. This selection is usually based
upon the anticipated presence of a chemical in a
medium from the site history and the chemical's
chemical and physical properties. If all areas of the site
in which a chemical is present have not been sampled,
small incremental risks either less than or equal to the
risk accounted for in the BRA may not be described,
although this approach is usually not feasible.
&
&
Uncertainty analysis gives the decision-maker a better
understanding of the implications and limitations of
the assessments
Locations sampled. The type of sampling strategy
selected may impact the uncertainty associated with the
results. For example, purposive sampling (sampling at
locations assumed to contain the
.
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&
&
&
chemicals) will likely result in a higher frequency of
chemical detection and concentration than random
sampling or systemized grid sampling. Therefore, use
of the results may skew the assessment toward greater
assumed exposures.
COPCs. Improper inclusion or exclusion of chemicals can
result in an underestimation (if inappropriately removed) or
overestimation (if inappropriately retained) of potential
health risks. Uncertainties associated with the selection
criteria include the following:
Number of samples. Fewer samples result in a higher
degree of uncertainty in the results. This is demonstrated in the summary statistics, specifically the 95%
UCL, in which the statistical descriptor (“t” or “H”
value), and hence the 95% UCL, increases with a
lesser number of samples. Planning for a specific
number of samples to reach a specific degree of
statistical confidence can limit the degree of uncertainty, although reduction may not be feasible and
quantifying the uncertainty may be just as effective in
defining risks.
&
Background comparison. If background measurements
are not truly representative of background conditions,
chemicals may be inappropriately retained or removed
from the list of COPCs.
&
Sample contamination. Uncertainty in the assessment
can occur if chemicals are not recognized as being
present as a result of sampling or laboratory
introduction and are included as COPCs.
&
Frequency of detection. Use of detection frequency as
a selection criterion may result in the inappropriate
exclusion of chemicals as COPCs.
Sampling process. The sampling process itself can
contribute to uncertainties in the data from a number
of factors, including sampling contamination (crosscontamination from other sample locations,
introduction of chemicals used in the field), poorly
conducted field procedures (poor filtering, incomplete
compositing), inappropriate sample storage (headspace left in containers of volatile sample containers,
inappropriate storage temperatures), sample loss or
breakage, and other factors. Some of these factors
can be controlled by an adequate SAP; however,
planning does not prevent the occurrence of sampling
errors.
Analytical methodology. The analytical methodology
can contribute to uncertainty in a number of ways,
including the chemicals analyzed (if analyses of all
important chemicals were not performed), the DLs or
QLs applied (if not sufficient), limitations in the
analysis due to matrix effects, chemical interferences,
poorly conducted analyses, and instrumentation
problems. Some of these factors can be addressed in
up-front planning (such as selection of the analytical
method), others cannot (instrumentation problems) be
mitigated.
4.7.2.2 Uncertainties Associated with Selection of
COPCs. Evaluation of the data to select COPCs for the
risk assessment may result in uncertainties. Application of
selection criteria may inadvertently result in an
inappropriate exclusion or inclusion of chemicals as
4.7.2.3 Uncertainties Associated with the Exposure
Assessment. Exposure estimates are associated with a
number of uncertainties that relate to the inherent variability
of the values for a given parameter (such as body weight)
and to uncertainty concerning the representativeness of the
assumptions and methods used.
&
Potential exposure pathways. Potential exposure
pathways are identified by examining the current and
future land uses of the site and the fate and transport
potential of the COPCs. While current land use and
potential exposure pathways are often easy to identify,
potential future uses can only be inferred from information available. For these reasons, sometimes the
most conservative potential future land use (i.e.,
residential) is often assumed in many assessments to
avoid underestimating potential health risks. This and
any assumption regarding future land use and exposure
pathways will add uncertainty to the assessment.
&
Potentially exposed receptors. As discussed above,
identification of potentially exposed receptors is based
upon information currently available. Assumed
exposed receptors under future use scenarios can only
be obtained from census projections, land planning,
and ownership records and can add uncertainty to the
assessment.
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&
&
&
Exposure and intake factors. Point values for
exposure estimates are commonly used in risk
assessments rather than a distribution of exposure
values that describe the distribution of exposures.
These values are usually conservative, and their use
results in introduction of conservatism into the risk
assessment. Conversely, use of average (CT) and the
upper end (RME) exposure and intake factors
describing a range of exposures may reduce this
conservativeness. Additionally, selection of sitespecific exposure and intake factors will lessen the
uncertainty to some degree, but since not all
potentially exposed receptors will be exposed to the
same degree, uncertainty cannot be eliminated.
Exposure point concentrations. Exposure point
concentrations are derived from measured site media
chemical concentrations alone and fate and transport
modeling. With regard to estimating exposure point
concentrations from sampling data alone, use of 95%
UCL and mean concentrations is associated with
some degree of uncertainty. The 95% UCL is used to
limit the uncertainty of estimating the true mean
concentration from the sample mean concentration.
This value may overestimate the true mean concentration. Use of the sample mean concentration may
under- or overestimate the true mean concentration.
Therefore it is strongly recommended that both values
are used to represent a range of exposure point
concentrations the population could potentially be
exposed to at the site.
Application of fate and transport modeling adds an
additional tier of potential uncertainty to exposure
point estimates. Models cannot predict “true”
exposure point concentrations at different times and
places or in different media, but provide an estimate
of the potential concentration under certain
assumptions. Often, the assumptions used in the
models are conservative to avoid underestimating
potential concentrations. In addition, not all applicable processes are or can be considered (e.g.,
degradation, removal processes). However it is even
more conservative to use current detected
concentrations for exposure point concentrations for
future use scenarios.
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4.7.2.4 Uncertainties
Associated
with
Toxicity
Assessment. EPA-derived toxicity values are recommended
to be used in risk assessments. These values are developed
by applying conservative assumptions and are intended to
protect even the most sensitive individuals in the
populations potentially exposed. Use of these values will
almost always result in overestimates of potential risk.
Factors that contribute to uncertainty include:
&
Use of uncertainty factors and modifying factors (MFs)
in the RfD. Noncarcinogenic RfDs are primarily
derived from animal toxicity studies performed at high
doses to which UFs or MFs (each usually a factor of
10) are applied. This process may remove the derived
dose many orders of magnitude from the dose which
caused the critical effect in the study, and will most
likely overestimate the site risks.
&
Use of an “upper bound” cancer SF. The SF is often
derived from high dose animal studies and extrapolated
to low doses using extrapolation models. The 95%
UCL of the slope predicted by the extrapolation model
is adopted as the SF. Use of this value results in an
upper bound estimate of potential risks.
&
Choice of study used to derive toxicity value. The
inclusion or exclusion of studies by EPA in the
derivation of a toxicity value is usually made by
professional judgment and affects the numerical
toxicity value.
&
The assumption of human sensitivity. When deriving
RfDs and SFs, EPA selects a critical study (usually the
animal study showing an adverse effect at the lowest
exposure or intake level) as the basis for deriving the
RfD or SF. EPA assumes that humans are at least as
sensitive as the most sensitive animal study.
4.7.2.5 Uncertainties
Associated
with
Risk
Characterization. EPA's standard algorithms are commonly
used to calculate chemical intakes and associated health
risks and hazards. There are certain assumptions inherent
in use of these equations that add uncertainty to the
assessment.
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&
&
Assumption of additivity. Calculation of both
carcinogenic risks and noncarcinogenic hazards
assumes (at least as a first-line approach) additivity of
toxic effects. This assumption adds uncertainty to the
assessment and may result in an overestimate or
underestimate of potential health risks, depending on
whether synergistic or antagonistic conditions might
apply.
Omission of certain factors. The standard algorithms
(without modification) do not consider certain factors,
such as absorption or matrix effects. In cases where
these processes are important, use of the standard
algorithms without modification may result in an
overestimate of potential chemical intakes.
4.7.3
Evaluation of Uncertainty.
Various
approaches can be applied to describe the uncertainties of
the assessment, ranging from descriptive to quantitative.
The method selected should be consistent with the level of
complexity of the assessment. It may be appropriate to
conduct an in-depth quantitative evaluation of uncertainty
for a detailed, complex assessment, but may not be
appropriate or even needed for a screening level or
relatively simple assessment. Qualitative and quantitative
approaches to expressing uncertainty are discussed below.
4.7.3.1 Qualitative Evaluation. A qualitative evaluation
of uncertainty is a descriptive discussion of the sources of
uncertainty in an assessment, an estimation of the degree
of uncertainty associated with each source (low, medium,
high), and an estimate of the direction of uncertainty
contributed by that source (under or overestimation). A
qualitative uncertainty assessment does not provide
alternate risk or hazard values, but does provide a
framework in which to place the risk and hazard estimates
generated in the assessment.
4.7.3.2 Quantitative Evaluation.
4.7.3.2.1
A quantitative uncertainty assessment is any
type of assessment in which the uncertainty is examined
quantitatively, and can take several forms. A sensitivity
analysis is a form of uncertainty analysis in which the
specific parameters are modified individually from which
the resultant alternate risks and hazard
estimates are derived. Probabilistic approaches, such as
MC simulations, are a more complex form of uncertainty
analyses, and examine the effect of uncertainty contributed
by a number of parameters.
4.7.3.2.2
A sensitivity analysis is a process of changing
one variable while leaving the others constant and
determining the effect on the output. These results are used
to identify the variables that have the greatest effect on
exposure. This analysis is performed in three steps:
&
Define the numerical range over which each parameter
varies.
&
Examine the relative impact that each parameter value
has on the risk and hazard estimates.
&
Calculate the approximate ratio of maximum and
minimum exposures obtained when range limits for a
given parameter are applied to the risk algorithm.
4.7.3.2.3
A probabilistic uncertainty analysis, such as
the MC simulation, examines the range of potential exposures associated with the distribution of values for input
parameters of the risk algorithm. Such methods can allow
the risk assessor to estimate both the uncertainty and
variability associated with various parameters of a risk
assessment. Uncertainty in these terms is defined as “a lack
of knowledge about specific factors, parameters, or models”
and variability as “observed differences attributable to true
heterogeneity of diversity in a population or exposure
parameter” (USEPA, 1997a).
In a probabilistic analysis, probability density functions are
assigned to each parameter, then values from these
distributions are selected and inserted into the exposure
equation. After this process is completed a number of
times, a distribution of predicted values is generated that
reflects the overall uncertainty of inputs to the calculation.
The results are presented graphically as the cumulative
exposure probability distribution curve. In this curve, the
exposure associated with the 50th percentile of the exposure
may be viewed as the “average” exposure and those
associated with the 90th or 99.9th percentile may be viewed
as “high end” exposure.
4.7.3.2.4
An MC simulation is performed in four steps:
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&
Assign probability distribution functions to selected
parameters in the risk algorithm.
&
Develop distributions for the selected parameters (if
not already available) and identify a number of
randomly chosen values within that distribution.
&
Apply the random input values for the parameters to
the risk algorithm, and generate a number of
randomly generated output values.
&
Develop a cumulative probability distribution curve
from the randomly generated output values.
4.7.3.2.5
A tiered approach should be used to
determine the complexity, cost, and time that the project
warrants for the probabilistic analysis, and whether one
needs to be performed at all. Results from a traditional
deterministic risk assessment should be examined prior to
performing a probabilistic analysis. If the risk is close to
the level of concern, the project may benefit from a
probabilistic analysis. If the site clearly requires, or does
not require action, further analysis is likely not necessary.
The risk assessor should discuss the insight to the risk
estimate that could be derived from further analysis with
the risk manager as they need to be balanced with costs
and time that the analysis will require.
4.7.3.2.6
A sensitivity analysis should be performed
on the results of the deterministic risk assessment to
determine which parameters should be focussed upon in
the probabilistic assessment. To effectively utilize
resources, those parameters whose uncertainty or
variability has the greatest impact on the risk estimate
should be assigned probability distributions in the MC
simulation, other less important parameters may be held
constant.
4.7.3.2.7
For more information on probabilistic
analysis, including recommendations for reporting
requirements, consult the Guiding Principles for Monte
Carlo Analysis (USEPA, 1997a) or access the EPA’s web
site at:
http ://www.ep a.gov/nceawww1 /mcp olicy.htm.
Additionally, EPA is in the process of developing RAGS
Part E, Supplemental Guidance to RAGS: The use of
Probabilistic Analysis in Risk Assessment. Several
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computer-based proprietary programs are available to
conduct this simulation.
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CHAPTER 5
5.2 DEVELOPMENT OF RGs
5.0 EVALUATING THE HHRA OF REMEDIAL
ALTERNATIVES
RGs are media-specific chemical concentrations that are
associated with acceptable levels of chemical intake. RGs,
sometimes also referred to as cleanup goals or TCLs, are
considered along with other factors such as ARARs in
identifying the chemical concentrations to which impacted
media are to be remediated. In general, RGs are developed
when the chemical-specific risks and hazards exceed
acceptable levels.
5.1 INTRODUCTION
The risk assessment methodology presented in Chapters 3
and 4 focused upon the performance of the screening risk
analysis used in the PA/SI, and the BRAs as appropriate
for RIs. This methodology serves as the framework for all
risk assessments. As mentioned earlier, risk assessments
may also be performed for other aspects of site activities.
One aspect is the performance of risk assessments to
support evaluations in the FS. As part of FS activities,
different remedial alternatives are examined from a
number of perspectives as part of the selection process.
The NCP specifies nine selection criteria to be examined
as part of remedial alternative evaluation: (1) protection of
human health and the environment, (2) compliance with
ARARs, (3) long-term effectiveness and permanence, (4)
reduction of toxicity/mobility/volume through treatment,
(5) short-term effectiveness, (6) implementability, (7) cost,
(8) state acceptance, and (9) community acceptance.
There are three risk assessment procedures that can be
applied to aid in the evaluation of remedial alternatives.
The three types of risk assessments are:
&
The development of RGs to be applied to site
cleanup.
&
The evaluation of long-term risks associated with the
alternatives.
&
The evaluation of short-term risks associated with
implementation of the remedy.
The first type is sometimes performed as a component of
the RI, but is distinguished herein because of its use in
selection of remedial options. The other two types are
useful in comparative evaluation of potential remedial
options. They are discussed individually below.
RGs differ from PRGs in that site-specific factors are
considered. PRGs are developed as a screening level tool
prior to the performance of an RI. Conversely, RGs are
developed from the site-specific BRA that was developed
during the RI. See RAGS Part B (USEPA, 1991d) for a
complete discussion of this process.
RGs Must be Developed and Applied in the
Context of Exposure Area and the Exposure Point
Concentration. It is Not Necessary to Remediate
All Media to or Below the RG.
Risk assessments are based on the 95% UCL of the
mean contaminant concentration. Calculation of an
RG establishes a firm number to be used for cleanup.
By requiring that all confimatory samples be below
the RG, excessive cleanup is done and results in
unnecessary cost escalation. A more realistic approach
is to evaluate an exposure area, calculating
concentrations that would result in a residual 95%
UCL equal to the RG. The calculation includes the
clean fill and the non- or minimally impacted areas.
This calculation should be done as part of the RD,
determining an adjusted RG. Additional information
can be obtained from Bowers, et al. (1996).
RGs should be based upon all significant exposure
pathways assessed in the BRA for that medium. However,
since the pathways resulting in the highest degree of
exposure will most greatly influence the RG, exposure
pathways that have minimal contribution to overall risks can
be excluded from the RG development with little or no
impact. In general, if a given exposure pathway contributes
less than 1 percent of the overall risks, it can be disregarded
in RG development.
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5.3 EVALUATION OF LONG-TERM RISKS
5.3.1
Comparative Risk Assessment of Remedial
Alternatives. For a remedial alternative to be acceptable,
it must be protective of human health and the environment.
However, more than one alternative may meet this criteria.
In these instances, an assessment of the long-term residual
risks associated with both alternatives can be developed as
a tool to assist in selecting an alternative. By comparing
the degree to which an alternative reduces potential risks
with other factors such as cost, acceptability, and effectiveness, one alternative may be preferable.
5.3.2
Risk Reduction. In addition to cost aspects, the
reduction of risk offered by the alternative should be
examined with respect to the risks estimated in the BRA.
If the risk reduction offered is not significant, or does not
address the primary risks identified in the baseline
assessment, these factors should be considered in the
remedy evaluation.
The reduction of risk offered by the alternative should also
be examined with respect to the size of the population
affected by the baseline risks or remedial alternative's
reduction of risk. Although protection of all receptors is
the primary goal, a modest reduction of risk for a large
population may be preferable to a large reduction of risk
for a small group.
5.3.3
Residual Risk. The potential risks to be
addressed in a risk analysis of the alternatives are those
remaining after the implementation and completion of the
remedial alternatives. The calculational methodology for
performing this type of the assessment is the same as for a
BRA. The potential exposure pathways and receptors
should also be the same as the BRA (unless temporal
factors modify some of the pathways or receptors). The
main factor that will change is the chemical concentration
(i.e., exposure point concentration) to which the receptors
may be exposed.
When developing an estimate of potential exposure point
concentrations after remediation, careful consideration
must be given to where remediation is to take place and
where no action is anticipated. It is not uncommon for
RAs to focus in some areas of a site, leaving others
untouched. Therefore, estimating the
5-2
potential exposure point concentration is not as simple as
assuming exposure to the RG, but will be a combination of
attaining the RG in some locations, being below the RG at
others, and perhaps exceeding the RG in some isolated
areas where (for some other valid reason) remediation is not
anticipated. The potential risks associated with different
combinations of remedial alternatives can be addressed by
examining each media separately, and then combining the
associated risks in modular fashion.
5.4 SHORT-TERM RISKS ASSOCIATED WITH
REMEDIATION
Another area in which risk assessment methodology can be
applied is the evaluation of short-term risks associated with
the implementation of each remedial alternative. The
objective of this assessment is to evaluate whether the RA
poses unacceptable potential risks to workers and other
nearby receptors for each alternative evaluated in the FS.
This type of risk assessment is distinct from the BRA, as
additional receptors may be exposed, and concentrations of
chemicals may also differ. Additional exposure pathways
may also exist. Depending on the length of time in which
the remedial alternative may be carried out, short- and/or
longer-term risks may need to be assessed.
This assessment focuses on the potential risks associated
with the implementation and operation of the alternative.
Therefore, an important component is to identify the
exposure pathways potentially associated with the
alternative. The risk assessor should work closely with the
design engineers to identify potential for the alternative to
result in exposure of workers or nearby populations.
Depending on the type of alternative, exposure could occur
through entrainment of soil (in the case of soil excavation),
volatilization (from air stripping), or other pathways.
Once the potential exposure pathways are identified, the
risk assessor needs to identify the potential degree of
exposure. Remedial designers may be able to provide
actual emission rates for certain alternatives. In other
instances, predictive modeling may need to be applied to
estimate exposure point concentrations. Once exposure
factors are identified, quantitation of potential risks is
calculated in the same manner as other risk assessments.
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If unacceptable risks are estimated for the alternative, the
use of control technologies or other management options
should be examined as risk reduction measures and/or
evaluation of other alternatives which may have less
potential to cause short-term risks. Examples of controls
include use of carbon filters on air strippers, dust
suppression, use of personal protection equipment, or
other controls that will reduce exposures. These factors
should be weighed with other FS criteria such as cost,
feasibility, schedule, risk reduction, etc., in choosing the
most appropriate alternatives.
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CHAPTER 6
6.0 RISK MANAGEMENT - INFORMATION
NEEDED FOR DECISION-MAKING
6.1 INTRODUCTION
The NAS defines risk management as "a process of
weighing policy alternatives and selecting the most
appropriate regulatory action, integrating the results of risk
assessment with engineering data and with social,
economic and political concerns to reach a decision"
(NRC, 1983). NAS has identified four key components
for managing risk and resources: public participation, risk
assessment, risk management, and public policy decisionmakers (NRC, 1994). Risk characterization is considered
the "bridge" or "interface" between risk assessment and
risk management. EPA recommends that risk
characterization should be clearly presented and separated
from any risk management considerations. EPA (1995a)
policy indicates that risk management options should be
developed using risk input and should be based on
consideration of all relevant factors, both scientific and
non-scientific.
Consistent with NAS, USACE has developed the HTRW
RMDM process. This process identifies factors to
consider when making decisions, developing and
recommending options, and documenting of risk
management decisions (Figures 6-1, 6-2). The process
establishes a framework to manage risk on a site-specific
basis. It emphasizes that risk management must consider
the strengths, limitations, and uncertainties inherent in the
risk assessment as well as other non-risk factors. The
consideration of risk is critical, since site actions are
driven by statutes and regulations which explicitly require
the "protection of human health and the environment."21
Need for Further Action; PA/SI and RFA
Has a release occurred ?
Need for Removal Action; the EE/CA
HHRA and Throughout Site Process
Time Critical: Is there an imminent health
threat; Non-time Critical: Is the removal
action appropriate and is it consistent with the
final action or remediation strategy?
Need for RA; the RI and RFI
Is the baseline risk acceptable? What are the
uncertainties?
Need for Mitigation of Short-Term Risks
Associated with Construction;
RD/RA;CMI
What is the exposure pathway of the risk?
What are the uncertainties? Will operational
and institutional control or engineering
modifications mitigate risks?
Risk and Non-risk Variables
to be Considered
Risk and Uncertainty; Budget; Schedule;
Competing Risk Reduction Priorities,
Compliance, Political, Economic, and Societal
Values of Resources to be protected
Figure 6-1. Inputs for Risk Management
Decision-Making, HTRW Project Decision Diagram
21
Examples of these requirements are 40 CFR
300.430(e)(1) of the NCP for deciding if RA is needed
for a CERCLA site; RCRA Sections 3004(u), 3004(v),
3008(h), 7003 and/or 3013 for requiring corrective actions
at hazardous waste TSD facilities to protect human health
and the environment; and the risk-based determination for
NFA (40 CFR 264.514) and selection of remedy (40 CFR
264.525) under the proposed Subpart S RCRA corrective
action rules.
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What is the project decision for the project phase?
Regulatory/Statutory Decision Statement
What are the inputs/study elements into the decision?
Comparison with health-based PRGs, screening risk assessment, BRA, risk analysis of
alternatives, development of RAOs
What are the anticipated options?
Interim measures, removal actions, ARARs
What are the risk and uncertainty?
Reasonable maximum/high-end; average; population; and probabilistic risks
What are other relevant non-risk factors?
Risk, Uncertainty, Budget, Schedule, Competing Risk Reduction Priorities,
Compliance, Political, Economic, and Societal Values of Resources to be protected,
Environmental Justice, and other Stakeholders' concerns.
What are the options?
An array of potential options and their ramification on the site decision
What is the recommended option?
And the rational for the recommended option.
Decision by the Customer and
Document Rationale for Decision
Figure 6-2. HTRW RMDM Process Flow Diagram.
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Therefore, selecting the proper risk tool and collecting data
to assess environmental risk is a primary responsibility of
the PM and the risk assessor.
The Risk Assessment Shall be Given, at a
Minimum, Equal Consideration with Other
Factors in the Risk Management Decision
Too often, we are performing non-risk driven
cleanups. Although many other factors enter into a
risk management decision, the safety and health of
the public, the workers, and the environment must
be considered foremost. Where a sound, defensible
risk assessment shows that there is little or no risk
from contaminants at a site, resources should not be
expended on additional study or remediation.
Additionally, data generated during the risk assessment
must not be used out of context. Risk screening values
must not be used as cleanup goals due to the
conservative parameters used in their generation. RGs
should be developed based on the calculations within
the risk assessment in conjunction with the risk
management decision regarding acceptable risks.
In addition to risk and uncertainty, there are many non-risk
variables influencing the risk management decision. The
major ones are cost, schedule, value of resources to be
protected, competing risk reduction priorities among sites
managed by the customer, compliance/regulatory, political,
economic, and technical feasibility. A relatively sensitive
political and/or economic factor to be considered is
"Environmental Justice or Equity." This phrase relates to
the government's initiatives to cleanup sites located in
"poor and disadvantaged" areas.
The risk assessment, in conjunction with other important
"non-risk" decision criteria, provides information on the
need for remedial or early actions. Therefore, a clear
understanding the risk assessment results and their
uncertainties is essential. Informed RMDM will lead to
protection of human health and the environment, cost
savings, meeting the agreed schedule, political harmony,
better management of resources, and other social and
economic benefits. The HTRW RMDM process is
consistent with recent initiatives by various officials:
Habicht (USEPA, 1992d), Denit (USEPA, 1993d),
Browner (USEPA, 1995c), and DOD (1994a) that suggest
the need for risk reduction based on "real world" or realistic
risk assessment, cost benefit analysis, and prioritization of
environmental issues.
Prior to gathering data and performing the HHRA, the PM
defines the site decision for the project phase, the required
study elements (types of HHRA or risk tools to be used),
and the potential uncertainties associated with the outputs
of the study element. Based on risk information and other
considerations, the customer can select from an array of
recommended risk management options. Options can
include gathering additional data, recommending NFA,
interim measures, or removal and/or RAs. To facilitate
RMDM, the USACE PM should anticipate potential risk
management options early in the project planning phase.
Examples of the use of risk assessment in various project
phases include:
&
PA/SI or RFA: A screening risk assessment and an
exposure pathways analysis may be performed to
determine the need for further investigations.
&
RI or RFI (prior to FS and CMS):
determines the need for the RA.
&
FS or CMS: Results of the BRA are used to develop
RGs (i.e., the calculation of a target chemical
concentration given a known target risk level or
acceptable hazard).
&
FS or CMS: Qualitative or quantitative risk
assessments to compare and evaluate potential health
impacts from the remedial alternatives. A qualitative
or simple quantitative risk assessment (similar to the
BRA) may be conducted to screen alternatives for
their potential short-term and residual risks.
&
RD (prior to conducting RA and CMI): Detailed risk
analysis may be performed to determine if protective
measures should be taken to minimize the impact to
health and the environment during remediation. For
example, a toxicity assessment may be conducted to
evaluate the short-term acute, subchronic, and chronic
toxicities of potential releases from the remediation
process.
The BRA
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It is important to recognize that risk managers often make
difficult decisions with considerable uncertainties in both
risk and non-risk information. Therefore, a focused and
balanced risk approach is recommended that recognizes the
reasonable limits of uncertainty for the protection of human
health and the environment as the primary consideration,
along with the considerations for non-risk issues. The risk
manager should clearly communicate the decision and the
associated assumptions, and document the basis for the
decision.
6.2 DETERMINING
ACTION
REQUIREMENTS
FOR
The fundamental requirement associated with any HTRW
response action is the “protection of human health and the
environment.”
This requirement focuses on the
acceptability of site risk or risks from the potential actions.
EPA risk assessment guidelines (USEPA, 1989j), the NCP
(USEPA, 1990c), and the proposed RCRA Corrective
Action Rule (USEPA, 1990d) define acceptable risks of
carcinogenic and noncarcinogenic effects. For carcinogens,
the acceptable individual upper bound lifetime risks range
from a probability of 1E-04 to 1E-06. For noncarcinogens,
the acceptable hazard, expressed in terms of the sum of
HQs for chemicals affecting similar organ systems or
toxicological endpoints (HI), is unity. Depending on the
exposure period of concern, the HQ is the average daily
intake divided by the chronic or subchronic RfDs which are
based on the No Observed Adverse Effects Level or the
Lowest Observed Adverse Effects Level in human study or
animal bioassays. Cancer risk is expressed as an individual
excess lifetime risk, and is the chronic daily intake
multiplied by the carcinogenic SF. Cancer risk or
noncancer hazard estimates are based on the CSM specific
for the site under baseline conditions, during site removal
or RAs, and after remediation. Human activity patterns
indicated in the CSMs are directly related to current and
future land use. This paragraph presents the risk
management options in key phases of the HTRW project
life cycle.
6.2.1
PA/SI and RFA. The purpose of PA/SI under
CERCLA and the RFA under RCRA is to identify if
chemical releases have occurred, or if the site can be
eliminated from further action. The PAs and RFAs are
typically performed by the state, EPA, or the Federal
agency, and are generally preliminary in nature. Under
6-4
some circumstances Federal agencies may perform these
activities with greater depth and vigor under EO 12580.
Unless good evidence exists that a site is contaminated, it
is a crucial for the PM to methodically review each
identified site, area of contamination, SWMU, and AOC,
and decide if these units should be eliminated from the next
project phase. In addition, it may be important to
determine if an imminent health threat or a substantial site
risk potentially exists that would require an early response
action (e.g., non-time critical removal actions, interim
measures, or IRA).
6.2.1.1 Actual or Potential Release/Exposure. Under the
PA/SI or RFA phase, the risk management decision will be
based on documented past spills and releases, the
likelihood of such spills/releases, the presence of
endangered or threatened species, sensitive environments
or resources to be protected, and the existence of transport
mechanisms that could bring the chemicals in contact with
receptors.
6.2.1.2 ATSDR Health Advisories.
The ATSDR
performs health assessments to document or provide
consultations on potential public health consequences
associated with hazardous waste or Superfund sites.
ATSDR representatives are located at all EPA regional
offices and work cooperatively with the Superfund and
RCRA staff.
ATSDR involvement in the
removal/emergency response program includes issuance of
draft and final health advisories or consultations.
Before ATSDR health advisories are used as a basis for
going forward into the next project phase or undertaking
removal actions, the HTRW risk managers and PMs should
contact the appropriate USACHPPM personnel for a
detailed review of the health advisories to ascertain the
strength and validity of the health advisories. This is
recommended because the PA/SI or RFA data are quite
tentative in nature, and oftentimes have not gone through a
vigorous data validation process. For example, if unfiltered
ground water data were used by ATSDR, and the samples
had high turbidity, indicating insufficient development and
purging of wells, the data should be questioned and, if
feasible, new ground water data acquired to assess the need
for RI, RFI, or potential removal actions.
In making risk management decisions concerning
emergency response actions in this project phase, the risk
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managers may be put in the position of accepting data or
recommendations of a lesser degree of confidence or a
higher degree of uncertainty.
6.2.1.3 Risk Screening and Prioritization of Units of
Concern. Initial risk screening (Chapter 3) is an important
tool for ranking or prioritizing sites (OUs/SWMUs). This
tool can result in substantial savings of resources, allowing
the implementation of a more focused site investigation.
The risk screening results are likely to provide significant
inputs into the RMDM for this project phase.22
It is not uncommon to have tens or hundreds of "sites" or
SWMUs within a site or facility boundary. Risk managers
at these facilities are faced with potentially complex
investigations. Rather than taking a "piece meal" approach
of investigation, the list of sites or SWMUs should be pared
down if possible. The risk manager may negotiate with the
agencies and enter in the IAG or FFA to permit the use of
an approach that "addresses the worst sites first," and at the
same time, group SWMUs within the same EUs or
geographical locations, as appropriate. This prioritization
should result in the greatest benefit with limited available
resources. Site prioritization should include the following:
22
EPA’s Deputy Administrator (USEPA, 1995a,c) is
concerned with the need for assuring consistency while
maintaining site-specific flexibility for making remedial
decisions (from site screening through final risk
management decisions) across programs. EPA stresses
that priority setting is reiterative throughout the decisionmaking process because limited resources do not permit
all contamination to be addressed at once or receive the
same level of regulatory oversight. EPA suggests that
remediation should be prioritized to limit serious risks to
human health and the environment first, and then restore
sites to current and reasonably expected future uses,
whenever such restorations are practicable, attainable,
and cost effective. EPA further suggests that in setting
cleanup goals for individual sites, we must balance our
desire to achieve permanent solutions and to preserve and
restore media as a resource, with growing recognition of
the magnitude of the universe of contaminated media and
the ability of some cleanup problems to interact with
another.
&
Eliminate sites or SWMUs administratively by record
review, interviews with current and former workers,
and ascertain whether the unit of concern meets the
definition of a "SWMU."
&
Conduct a site reconnaissance and group sites or
SWMUs with common exposure pathways or EUs, if
appropriate.
&
Rank the remaining sites or groups of sites
qualitatively or quantitatively based on the CSM or a
screening risk analysis.
Generally, the above tools will serve well if they are
objectively and uniformly applied. The use of site
prioritization:
&
Provides justification for NFA for low priority sites.
&
Allows better resource allocation for investigation of
the remaining sites.
&
Helps identify potential boundaries where receptors
are to be protected.
&
Identifies high priority sites or SWMUs for emergency
response, early actions, or accelerated cleanup or site
stabilization.
The Relative Risk Site Evaluation Primer (DOD, 1994b)
recommends evaluation based on three criteria: (1)
contaminant hazard factor, (2) migration pathway factor,
and (3) receptor factor. Information generated from the
initial risk screening (Chapter 3) can be used as a decisionmaking basis using a similar site ranking process. Sites
may be ranked high, medium, or low based on nonquantitative exposure pathway considerations such as the
following:
1.
Significant Contaminant Levels
a.
High Relative Risk: Sites with complete pathways
(contamination in the media is moving away from
the source) or potentially complete pathways in
combination with identified receptor or potential
receptors.
b.
Low Relative Risk: Sites with confined pathways
(i.e., contaminants not likely to be
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released or transported) and limited potential for
receptors.
c.
Medium Relative Risk: Sites with characteristics
not indicated in the above.
2.
Moderate Contaminant Levels
a.
High Relative Risk: Sites with complete pathways
or potentially complete pathways in combination
with identified receptors; or sites with complete
pathways in combination with potential receptors.
assessment tools to satisfy the information needs, and risk
management options are presented in this section. "Nonrisk" factors to be considered in the decision-making are
presented in Section 6.2.4.
Risk Management Decision
&
Risk Management Options/Rationale
&
b.
Low Relative Risk: Sites with confined pathways
and any receptor types (i.e., identified, potential,
or limited potential), or sites with potentially
complete pathways in combination with limited
potential for receptors.
NFA
Medium Relative Risk: Sites with characteristics
not indicated in 2.a and 2.b above.
Rationale:
3.
Minimum Contaminant Levels
&
a.
High Relative Risk: Sites with complete pathways
in combination with identified receptors.
No knowledge of documented releases or major
spills/low likelihood of spills/procedures existed to
promptly cleanup all spills.
&
b.
Medium Relative Risk: Sites with potentially
complete pathways in combination with identified
receptors or sites with evident pathway in
combination with potential receptors.
Transport mechanisms do not exist, e.g., presence of
secondary containment.
&
The substances released are not expected to be present
due to degradation and attenuation under the forces of
the nature.
&
Spills or releases have been addressed by other
regulatory programs (e.g., the UST program or RCRA
closure under Subpart G of 40 CFR 264 or 265).
&
The unit does not meet the definition of a "SWMU."
&
The unit is part of another identified unit or site which
will be addressed separately.
c.
Low Relative Risk: Sites with characteristics not
indicated in 3.a and 3.b above.
The relative risk site ranking process may also be modified
to include consideration of the degree of confidence in the
relative risk rating. Sites with a low degree of confidence
and a low relative risk may then be given a higher rating
than sites with a high degree of confidence and a low
degree of risk.
6.2.1.4 Risk Management Decisions and Options. Risk
management decisions, risk information needs, risk
6-6
Further Evaluation Needed
Rationale: If a site cannot be justified for NFA, further
evaluation (Expanded SI; Extent of Contamination Study;
RI or RFI) will be needed.
&
c.
Should a site be eliminated from further investigation
or included in the RI or RFI project phase?
Although risk assessment is traditionally performed in the
RI or RFI project phases of HTRW response actions, risk
assessment can assist the risk managers in all project
phases. Results of risk assessment activities are used to
answer three key questions:
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&
Whether or not there is a need to go forward with the
next project phase.
&
Whether or not early response actions (removal
actions, interim measures, or IRAs) should be taken to
mitigate potential risks.
&
Effectiveness of the potential response action and the
short-term risks associated with implementation of the
removal actions.23
it is questionable whether the levels pose
unacceptable chronic risk or hazard.
&
Site contaminants are not likely to be persistent or the
contaminants are relatively immobile.
&
Early Response Action
Rationale:
&
There is no current impact, but if uncontrolled, the site
could pose a substantial threat or endangerment to
humans or the environment. (Examples are: physical
hazard, acute risk from direct contact with media of
the unit or site, or effluents or contaminated media are
continuously being discharged to a sensitive
environment.)
&
The principal threat has reasonably been identified
because of the evidence of adverse impacts. In this
context, the COPCs are known and the exposure
pathways are judged to be complete, e.g., the exposure
point or medium has been shown to contain the
COPCs.
&
The boundary of contamination is reasonably well
defined so that removal action(s) can be readily
implemented.
&
The early actions are consistent with the preferred final
remedy anticipated by the customer, reducing risks to
human or ecological receptors, or both.
&
The response action will be used to demonstrate
cessation or cleanup of releases, resulting in
substantial environmental gain which is the basis for
early site close-out or further investigation.
&
High concentration (acute hazard level) of site
contaminant is found in the exposure medium.
&
Highly toxic chemicals or highly persistent and
bioaccumulative chemicals found on-site which may
be transported off-site.
Risk Management Decision
&
Should early response action be undertaken to mitigate
risk?
Risk Management Options/Rationale
&
No Early Response Action
Rationale:
&
&
Transport mechanisms probably do not exist, e.g.,
presence of secondary containment.
Low concentration of site contaminants or the levels
measured probably do not pose an acute hazard, and
23
Removal actions must be flexible and tailored to specific
needs of each site and applicability (i.e., complexity and
consistency should be used in evaluating whether non-time
critical removal actions are appropriate). Examples of
removal actions are: (1) sampling drums, storage tanks,
lagoons, surface water, ground water and the surrounding
soil and air; (2) installing security fences and providing
other security measures; (3) removing and disposing of
containers and contaminated debris; (4) excavating
contaminated soil and debris, and restoring the site (e.g.,
stabilization and providing a temporary landfill cap); (5)
pumping out contaminated liquids from overflowing
lagoons; (6) collecting contaminants through drainage
systems (e.g., french drains or skimming devices); (7)
providing alternate water supplies; (8) installing
decontamination devices (e.g., air strippers to remove
VOCs in residential homes); and (9) evacuating threatened
individuals, and providing temporary shelter or relocation
for these individuals (USEPA, 1990f).
&
Non-complex site (no cost recovery issue, limited
exposure pathways, small area sites, etc.).
Early response actions or removal actions, consistent with
the final RA, may be taken at any time to prevent,
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limit, or mitigate the impact of a release. To encourage
early site closeout or cleanup, EPA has encouraged early
response actions at sites where such actions are justified.
To the extent possible the selected removal actions must
contribute to the efficient performance of long-term RAs.
EPA's RCRA Corrective Action Stabilization Technologies
(USEPA, 1992n) and SACM (USEPA, 1992g) emphasizes
controlling exposure and preventing further contaminant
migration. While these concepts are intended to expedite
site actions, risk assessment provides important information
for justifying cleanup actions. The applicable risk
assessment methods include:
Early actions or accelerated cleanup can often be justified
as long as the actions are consistent with the preferred site
remedy. Since remedies are generally not selected until late
in the FS or CMS, the customer's concept of site closeout
and anticipated action is critical for deciding which types of
early actions are appropriate. Based on experience gained
in the Superfund program, EPA has identified certain site
types where final remedies are anticipated to be the same
(presumptive remedies). The current list of presumptive
remedies includes:
&
Municipal landfill - capping and ground water
monitoring.
&
A screening risk analysis.
&
&
Development of medium-specific short-term health
goals for screening or comparison with modeled or site
data.
Wood treatment facility - soil and ground water
remediation.
&
Ground water contamination with VOCs - air
stripping/capture wells.
Qualitative evaluation of removal actions for their
effectiveness to reduce exposure and risks.
&
Soil contamination with VOCs - soil vapor extraction.
&
&
BRA may be appropriate for non-time-critical removal
action and for complex sites (sites with multiple
pathways, without ARARs, large geographic areas,
and with a need for cost recovery).
In order to allow timely input into the RMDM for the
removal actions or interim corrective measures, the risk
assessment or risk analysis should be planned and
conducted in a timely manner. If removal actions are
straightforward, e.g., addressing hot spot areas or high
concentration plumes, the risks associated with removal
actions will then be evaluated for their potential short-term
risks and hazards for the specific removal actions. The
short-term risks or threats to workers and other human
receptors may be based on one or more of the following:
&
Air, soil, surface water, ground water (including
drinking water), and food chain contamination.
&
Direct (dermal) contact with contaminated media.
&
Ingestion of contaminated media or inhalation of
contaminated air or particulate matter.
&
Fire/explosion hazard.
6-8
6.2.1.5 Qualitative Evaluation of Response Actions for
Their Effectiveness to Reduce Risks. Removal of hot spots
can provide substantial improvements in the site
environment. In some cases, actions can drastically reduce
exposure to receptors and allow natural attenuation to
further reduce the exposure point concentration. If removal
actions are needed, the risk manager should request two
types of risk information. First, if there is more than one
removal option, what is the comparative effectiveness of
the options to reduce exposure and risks? Second, what is
the risk or environmental impact associated with the
proposed removal action? To answer the first question, the
HTRW risk assessor or risk manager provides information
on how the removal option can eliminate risk or reduce the
level of exposure both on-site and off-site, if contaminant
migration has occurred to off-site exposure points. If
substantial risk reduction can be obtained by all options,
the risk manager should consider other factors, such as
effectiveness, reliability, etc. To answer the second
question, the project engineer estimates the destruction or
treatment efficiency of the medium to be treated or
disposed, and the type/quantity of wastes or contaminated
debris to be generated for each potential option. This
information is important if an action is
EM 200-1-4
31 Jan 99
likely to generate waste or damage sensitive environments
in the course of the remediation.
If the Cumulative Site Risk Calculated in the
BRA Does Not Exceed 1E-04 for Reasonable
Exposure Scenarios, ARARs are Not Exceeded,
and Ecological Impacts are Not Significant, No
RA Should be Required.
It is important to communicate and obtain an early buy-in
of the removal action from the local community. If the
proposed removal actions are likely to pose unacceptable
short-term risks to on-site or off-site receptors, the removal
action should either be discarded or monitoring/control
measures be instituted. (As discussed later, the risk
assessor and HTRW TPP team members provide options
for making decisions when there are divergent interests
between the protection of humans and the protection of
ecological receptors of concern.) The risk assessor should
work with other project team members to evaluate the
potential for chemical releases or habitat destruction
potentially associated with a remedial option. These
evaluations should be qualitative and not extensive, and can
be based on a consensus of professional judgement/opinion.
These individuals should recommend alternatives or
precautionary/protective measures to the risk manager to
mitigate any potential risks.
6.2.2
RI/RFI. The primary objective of RFI, RI, or
other equivalent HTRW project phases is to determine if
site contamination could pose potentially unacceptable
human health or environmental risks. Determination of
unacceptable risk, according to the NCP, is identified
through a BRA under RME. The RCRA corrective action
process is similar to Superfund for determining the need for
remediation, albeit initially, the TSDF owner/operator may
simply compare a specific set of SWMU data with
established health-based criteria. EPA generally considers
performance of a HEA to be functionally equivalent to the
Superfund BRA (both human health and ecological) in the
RI/FS. While a few EPA regions have developed separate
guidelines for RCRA, there is a national effort underway as
well. The RCRA HEA should be conducted prior to or
early in the CMS to determine the need for corrective
measure implementation.
Remediation beyond risk levels has resulted in the
expenditure of excessive tax dollars.
Where
remediation is not justified by risk or the exceedance
of ARARs, it should not be done. This point is
summarized by EPA: “Where the cumulative
carcinogenic site risk to an individual based on
reasonable maximum exposure for both current and
future land use is lass than 1E-04, and the noncarcinogenic HQ is less than 1, action generally is
not warranted unless there are adverse environmental
impacts.” (USEPA, 1991a)
The BRA or HEA associated with the RI/RFI project phase
can assist the RMDM process in the following ways:
&
The BRA, performed in the RI/FS or RFI project
phase, presents the degree of potential carcinogenic
risks and noncarcinogenic hazards posed by the site to
humans (individuals and populations), and the
associated uncertainty. Risks can be estimated for the
entire site, OUs, AOCs, and SWMUs.
&
The results of the BRA can be used to answer the
questions relating to the site decisions on: (1) whether
or not there is a need to go forward with the next
project phase (i.e., RD/RA needed or no action
alternative); and (2) whether or not removal actions
(interim corrective measures) should be implemented
to mitigate potential risks, which are consistent with
final action.
&
If a site poses unacceptable chronic hazard or
carcinogenic risk, remediation will be needed for
pathways indicated in EUs. Pathways/EUs which do
not pose an unacceptable risk may be eliminated from
further concern. The algorithms developed in the
BRA can be used in reverse to develop site-specific
health-based RGs (cleanup levels) in the FS.
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The above determinative factors are considered in the
review of the BRA summary (and uncertainty) by the risk
manager, along with other non-risk criteria in the RMDM.
It should be noted that the decision could be partial, i.e.,
some SWMUs or sites within the facility will require
remediation/removal actions while others do not.
&
High concentration (acute hazard level) of site
contaminant is found in the exposure medium.
&
Highly toxic chemicals or potent carcinogens are
found onsite which may be transported offsite.
&
Documented unacceptable drinking water or surface
water contamination, which is contacted or consumed
by humans.
&
Non-Time-Critical Removal Action, Interim
Corrective Measures, or Accelerated Cleanup
Risk Management Decision
&
Should RA or corrective measure be required based
on the BRA?
Risk Management Options/Rationale
Rationale:
&
NFA Needed
&
Principal threat to human health has been identified.
If unabated, there is a potential of injury, chronic risk
to humans or the environment.
No acute or chronic hazards of risks to humans under
current and future exposure (land use) conditions/low
likelihood of exposure by the receptors.
&
Presumptive remedies available for the identified sites
or SWMUs.
&
Transport mechanisms probably do not exist.
&
Transport mechanisms are available.
&
Low concentration of site contaminants or the levels
measured probably do not pose acute and chronic
hazard and carcinogenic risk.
&
The exposure pathway was the basis for NPL listing,
or past or ongoing enforcement actions on spills or
releases.
&
There is no anticipated risk of physical hazards.
&
&
Site contaminants are not likely to be persistent or the
contaminants are relatively immobile.
The response action is generally consistent with the
preferred site remedy, and there are no complicating
factors.
&
&
Technically not feasible or impractical (e.g., dense
non-aqueous phase liquid) in an aquifer not
anticipated to be used for human consumption.
Control of migration should be taken soon, or risk the
exposure of site chemicals to human receptors or valuable community resources.
&
&
Time-Critical Emergency Response Action Needed
The early action will result in an incremental gain in
environment benefit (including ecological), plus
substantial savings in future remediation expense.
&
FS (CMS) Remediation Warranted
Rationale:
&
Rationale:
&
A high likelihood of releases and transport of site
contaminants to receptors, e.g., ground water plume is
migrating to onsite or offsite drinking water wells.
Rationale:
&
&
A high risk of physical hazards.
6-10
Unacceptable hazards and risks involving multiple
chemicals and exposure pathways. If unremediated,
there is a long-term threat to humans and other
resources.
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&
Transport mechanisms are available.
&
Site-specific conditions (geology or location, etc.) are
unique or unusual and require detailed evaluation of
remedies.
&
Unusual chemicals present on site which will require
bench-scale and pilot-scale studies.
decision-makers, including an array of remedies for
selection, RAOs, or TCLs for verification of cleanup.24 The
selected remedies/TCLs or revisions thereof will be entered
into the ROD or the Part B permit.
Risk Management Decision
&
NFA Needed Except Periodic or Continuous
Monitoring
Rationale:
&
RCRA facility is operating and expected to continue
for the anticipated future.
&
Interim corrective measures or removal actions in
place which have effectively controlled migration of
site contaminants and exposure.
&
Baseline risk estimates are within the acceptable
range and the exposure (land use) remains in the
anticipated future.
&
Institutional controls are deemed adequate to control
exposure.
&
&
Toxicity of the COC, which causes the principal threat
is tentative, albeit the risk or hazard has been
exceeded.
The baseline risk estimates are uncertain and there are
no readily available transport media for exposure (e.g.,
public water supply is available in the area) or COCs
are subject to natural dilution and attenuation.
6.2.3
FS/CMS and RD/RA. The FS or CMS is
triggered when the baseline risk is unacceptable and
remediation is needed to mitigate risks and prevent further
contaminant migration. In some instances, the FS or CMS
could be driven by a legal requirement to meet ARARs,
although ARARs are not necessarily risk-based. The FS or
CMS evaluates potential remedial alternatives according to
established criteria in order to identify the appropriate
remedial alternative(s). The FS or CMS can be performed
for the entire site or any portion of the site that poses
unacceptable risks. The results of the FS/CMS include
recommendations for the risk managers or site
&
What are the RAOs?
Risk Management Options/Rationale
The risk management decision for selection of final
remedies depends substantially on the RAOs. Uses of
RAOs are summarized below:
&
Developed or agreed upon by the agencies prior to the
FS or signing of the ROD (or modification of the
RCRA permit), RAOs are used to evaluate the
feasibility of candidate remediation technology in the
FS.
&
Initial estimation and costing of remediation (e.g.,
excavation and stabilization).
&
Delineation of cut lines for remediation.
&
For use in negotiation or final determination of specific
areas, SWMUs or site-wide cleanup goals, by
considering uncertainties, technology, and cost.
Before embarking on an FS, RAOs should be developed
using site-specific risk information consistent with site
conditions. Factors to be considered when RAOs are used
as the basis for designing and implementing remediation
are presented below:
6.2.3.1 RAOs Must be Based on CSM. The CSM
provides the framework for the BRA and identifies the
specific pathways of concern. RAOs must be able to
24
For the purpose of protecting the environment, the
TCLs (sometimes known as RAOs) may be the same as
the environmental-based preliminary remediation levels,
or they may be different. TCLs or RAOs are negotiated
levels for verification of the proposed cleanup technology,
practical QLs (PQLs), and uncertainties associated with the
preliminary remediation levels to protect ecological
resources of concern.
6-11
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31 Jan 99
address these pathways and the associated risks. A refined
CSM, based on the results of the BRA is paramount to the
establishment of focused RAOs. The RAOs are based on
preliminary remediation levels developed as the project
strategy goals in Phase I of the HTRW project planning
under RI/FS or RFI/CMS.
6.2.3.2 RGs Must Be Protective and Practical. RGs are
performance and numerical objectives developed in the
FS/CMS to assure that the remedial alternative will
contribute to site remediation, restoration, and closeout/
delisting. As such, they must be protective and workable.
To assure protectiveness, risk-based RGs should be first
derived using the BRA procedures in reverse (USEPA,
1991d). The uncertainty associated with development of
the RGs should be discussed and quantified. Site decisionmakers carefully consider technology, PQLs, ARARs, or
TBC criteria, reference location concentrations, acceptable
hazards, field or laboratory analytical uncertainties, etc.,
before setting the RAOs.25
6.2.3.3 Action Must Be Consistent with Other Project
Phases. Understanding of the nature and extent of
contamination, as well as the media and exposure pathways
of concern, is a critical requirement for successful
completion of the FS or CMS and remedy selection.
Therefore, data used in the FS or CMS must interface with
the RI/RFI and other previously collected site data.
Inadequate data or data of poor quality misrepresent site
contamination and may lead to an inadequate BRA and FS.
For each exposure pathway that presents an unacceptable
risk, the risk assessor and the appropriate project team
members (e.g., chemist, geologist, or hydrogeologist)
should review the RI data before conducting the FS. This
is particularly important when the FS is performed
simultaneously with the RI, based on assumptions and
PA/SI or RFA data.
25
Certain sites may be contaminated with natural or
anthropogenic substances which pose matrix interferences
and cause high sample DLs (i.e., the QLs may be higher
than the environmental-based PRGs). For these sites, it
may be advantageous to design a representative sampling
program of the background medium to establish QLs for
use as alternative RGs.
6-12
Minimal information or guidance has been developed by
EPA regarding the development of RAOs for RCRA and
Superfund sites. RCRA has issued the ACL Guidance
based on 264.94(b) criteria and case studies (USEPA,
1988f) which may be applied to developing ACLs at the
source if the acceptable ground water/surface water mixing
zone concentrations and the dilution/attenuation factors are
defined. Under the proposed Subpart S rule for RCRA
corrective action, the state water quality criteria can be
used to screen if a CMS should be conducted. Nonetheless,
the key risk management issue concerning the above is that
the cleanup goals must be practical and verifiable. When
cleanup goals are developed to protect both humans and
ecological receptors, according to Section 300.340 of the
NCP, the goals must be so adjusted that both receptor types
are protected.
Environmental and human health-based RAOs should be
developed together and proposed to the risk manager and
agencies for use in the CMS for the evaluation of remedial
alternatives. It should be noted that the RAOs may have to
be revised or refined based on other considerations, e.g.,
technology, matrix effects, target risks, uncertainties, and
costs (associated with the extent of the remediation,
management of remediation wastes, cost of cleanup
verification analyses).
Risk Management Decision
&
What are the Remedial Alternatives or Corrective
Measures?
&
What are the Preferred or Optimal Remedial
Alternatives?
Risk Management Options/Rationale
In addition to a cost and engineering evaluation of the
potential remedial alternatives, each alternative must be
evaluated for its ability to reduce site risk. Among the nine
criteria identified by the NCP for remedy selection,
protection of human health and the environment and
satisfying ARARs are considered to be the threshold
(fundamental) criteria which must be met by any selected
remedy. More recently, EPA has placed increased
emphasis on short- and long-term reliability, cost, and
stakeholders' acceptance in the overall goal to select
remedies. Therefore, the assessment of residual risk (a
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31 Jan 99
measure of the extent of site risk reduction) is a critical
task.
to conducting the screening evaluation of remedial
alternatives includes:
Screening and detailed analyses of remedial alternatives
will be conducted in the FS and CMS project phase. The
preferred remedial alternative will be proposed. As
warranted, analysis of short-term risks to assess the need
for control measures will be conducted in the RD project
phase, and the control measure(s), if appropriate, will also
be proposed.
&
Identity and quantity of emissions, effluent,
byproducts, treatment residues, which may be released
to the environment (during normal start-up and shutdown operations).
&
Toxicity of chemical substances or COCs in the above
discharges.
In the FS, potential risk reductions associated with remedial
alternatives are assessed. The relative success of one
alternative over another is simply the ratio of the residual
COC concentrations in the exposure medium of concern.
This screening evaluation does not take into account shortterm risks posed by the alternative or technology due to
acute hazards, releases, or spills.
&
Potential for dilution and attenuation.
&
Existence of exposure pathways and likelihood of the
pathways to be significant and complete.
&
Potential for spill or releases during remediation,
material handling, storage and transportation of
remediation wastes.
&
Potential for the causation of non-chemical
environmental stressors such as destruction of critical
habitat for threatened and endangered species,
wetlands, or other sensitive environments.
&
Temporal attributes associated with a RA which could
be altered to reduce the action's impact.
&
Potential release of additional COCs to the
environment (e.g., re-suspension of toxic sediments
during dredging, and changes of pH, redox potential,
oxygen, and chemical state that may increase solubility
and bioavailability).
6.2.3.4 Screening Evaluation of Alternatives. This
evaluation focuses on determination of short-term risks
posed by the removal or remedial alternatives. The
findings of this evaluation are compared among the
alternatives to determine preferred remedies based on the
effectiveness of the remedies to satisfy RAOs with the least
impact. This screening evaluation should focus primarily
on effectiveness, risk reduction, and cost.
Risk screening of alternatives should generally be
qualitative or semi-quantitative. If a remedy has already
been selected or is highly desirable for selection, a detailed
risk analysis may not be needed. Instead, the evaluation
should focus on the risk reduction of the preferred remedy,
and identify any concerns or data gaps which need to be
addressed. The data needed to perform this screening
evaluation may come from many sources: RI or RFI data,
bench scale or pilot scale treatability studies conducted for
the site or from comparable sites, compatibility test, test of
hazardous characteristics, field monitoring measurements,
vendor's or manufacturer's information, literature values,
and professional judgment.26 Key information needed prior
The following are lists of qualitative evaluation criteria:
&
Risk Reduction Attributes (environmental
protection, permanence, and toxicity reduction)
&
Able to remove, contain or effectively treat site COCs.
26
The bench scale or pilot scale treatability studies may
provide valuable information for the estimation of remedial
action or residual risks. Treatability studies provide data or
information on the degree of removal and/or destruction of
the COCs, quantity and identity of chemicals in the
emissions or effluent discharges, and potential treatment
standards to be applied to satisfy RAOs. This information
is important to quantify the magnitude of risk reduction and
will be useful in the comparative analysis of potential
remedial alternatives.
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31 Jan 99
&
Able to address the exposure pathways and media of
concern.
&
Able to meet the RAOs and overall project strategy
goals.
&
Assessment of Residual Risk Potential
&
Reasonable anticipated future land use.
&
Quantity of residues or discharges to remain on site.
&
Toxicological properties of the residues.
&
Release potential of residues based on their
fate/transport properties (e.g., log octanol/water
partition coefficient, water solubilities, vapor pressure,
density, etc.).
&
Properties or characteristics of the environmental
medium which facilitate transport (e.g., hydraulic
conductivity, organic carbon contents, wind speed and
direction, etc.).
&
Potential for dilution and attenuation for residues
released into the environment.
&
This evaluation may be qualitative, semi-quantitative, or
quantitative. If the analysis is quantitative, procedures and
approaches similar to the BRA may be followed. The
Air/Superfund National Technical Guidance Study Series
(USEPA, 1989a, 1990d, 1992o, 1993c, and 1995b)
includes documents providing guidance for rapid
assessment of exposure and risk. For example, guidance on
determining the volume of soil particulates generated
during excavation is provided in Estimation of Air Impacts
for the Excavation of Contaminated Soil (USEPA,
1992b). The data sources used to perform this risk analysis
task should be similar to those identified for the screening
evaluation of remedial alternatives. Although it is
conceivable that the level of effort required for this analysis
may be high (particularly if the same analysis has to be
performed for a number of preferred remedies), it is
anticipated that the documentation and report writing will
be focused and streamlined.
The report should focus on the risk analysis approaches,
sources of data, findings/recommendations for risk
mitigation measures, and appendices. Key factors or
criteria to be considered in the screening evaluation of
remedial alternatives are:
&
The criteria or considerations in the assessment of
short-term and residual risks are substantially similar
to those identified for the screening evaluation of
remedial alternatives. The key difference may be
additional use of quantitative data input into the risk
calculations, e.g., sediment transport modeling to
evaluate the potential for migration of toxic sediment,
amount
of
discharges
or
emissions,
dilution/attenuation or atmospheric dispersion factors,
exposure frequency, duration, and other activity
patterns which could impact existing vegetation and
wild life in time and space.
&
Time required and extent of recovery from exposure to
the COCs.
&
The potential for fire, explosion, spill, and release of
COCs from management practice of excavated or
dredged materials should remain qualitative or semiquantitative. Fault-tree (engineering) analysis for
accidental events may be attempted under special
circumstances (e.g., to address public comments or if
demanded by citizens during public hearing of the
proposed remedies).
The extent of, and permanence of, remediation, habitat
destruction and alteration; e.g. the construction of an
access road through wetlands would be considered
permanent.
6.2.3.5 Detailed Analysis of Alternatives. Detailed
analysis is usually conducted for the preferred remedial
alternatives (or removal actions) identified in the screening
evaluation described above. This detailed analysis has
three objectives: (a) detailed assessment of potential shortterm risk during RA, and residual risks if appropriate; (b)
assess the potential for the risks to be magnified due to
simultaneous implementation of this and other preferred
alternatives; and (c) identify potential risk mitigation
measures for the preferred remedies. The findings of these
tasks are presented for final selection of remedies prior to
ROD sign-off or RCRA Part B permit modification. All
preferred remedies or options should satisfy RGs and
should pose minimum health and environmental impact.
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6.2.3.6 Risks from Simultaneous Implementation of
Preferred Remedies.
&
Common exposure pathways for effluent or discharges
from remedies.
&
Period of exposure to receptors via the common
locations, time, and pathways.
&
Sensitive environments and other threatened or
sensitive wildlife or aquatic populations.
&
Risk estimates or characterization results.
&
Toxicological evaluation for the validity of additivity
of risk (e.g., under the Quotient Method), based on
literature review, mode of action, and common target
organs, etc.
&
Qualitative or quantitative assessment of potential
short-term or residual risks.
completion of the RA. The COC residuals could either
remain or be quickly degraded, depending on the COC's
physical and chemical properties. The level of residual risk
will depend on the effectiveness of the remedy in
containing, treating or removing site contaminants, and the
quantity, and physical, chemical, and toxicological
characteristics of residues or byproducts remaining at the
site. Site COCs which remain on-site after the RA should
be assessed for their potential risks.
This evaluation step focuses on a risk reduction assessment
to determine if a potential remedial alternative is able to
meet the RAOs, and an assessment of residual risk
potential. The findings of these tasks are compared among
the alternatives to determine an array of preferred remedies
based on the effectiveness of the remedies to satisfy RAOs
with the least long-term health and environmental impacts.
RA/Residual Risks vs. Baseline Risk
Short-Term Risks Associated with Construction; the
Design Risk Analysis
All removal or remedial alternatives have a potential to
pose short-term risks to on-site mitigation workers,
ecological receptors, and off-site humans. Risks may be
associated with vapors, airborne particles, treatment
effluent, resuspension of sediment resulting in an increase
in the total suspended solids or siltation of substrate for
macroinvertebrates, and residues generated during
operation of the remedial alternative. Therefore, all the
alternatives should be reviewed for their short-term risks in
conjunction with data from their bench scale or pilot scale
treatability studies or data from implementation of the
remedy at comparable sites. The risk assessor should
estimate the period of recovery from these short-term
insults and determine if biological or chemical monitoring
of the effects of remediation activities should be
implemented. For all practical purposes, risk may remain
upon completion of the RA (residual risk).
Long-Term Risks Associated with Alternatives; the
Residual Risks
Unless all sources of contamination are removed or
isolated, there will be residual risks at the site upon
There are notable differences between RA/residual risks
and the baseline risk. The key difference is that baseline
risk refers to the potential risk to receptors under the "no
remedial action" alternative, and RA and residual risks
refer to short-term risks during RA and long-term risks
which may remain after completion of the RA, respectively.
Residual risk may be considered comparable to baseline
risk after remediation, since in both cases the risks are
chronic or subchronic in nature. RA risks are generally
short-term (acute or subchronic) risks.27
6.2.4
Non-Risk Issues or Criteria as Determining
Factors for Actions. The NCP recognizes that it is not
possible to achieve zero risk in environmental cleanup;
therefore, the approach taken by Superfund is to accept
27
One exception (i.e., remedial risk which is long-term)
is a pump-and-treat remedy of ground water to meet
MCLs for organics which pose a threat to human health
but not ecological receptors. If the effluent is discharged
to a surface water body and happens to contain trace
elements at high levels (or other COCs not reduced by
the treatment process), then an exposure route to
environmental receptors may remain which is not
addressed by the BRA, and which will exist for the
operational lifetime of the remedy.
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non-zero risk and return the site to its best current use (not
to conditions of a pre-industrialization era). Under RCRA,
the preamble to the proposed Subpart S recognizes that
cleanup beyond the current industrial land use should be
justified. This section presents and discusses the non-risk
factors, and recommends a balanced approach for
resolution of issues to enable quality RMDM. These
factors can be categorized into scientific and non-scientific
factors, as explained below.
6.2.4.1 Scientific Factors.
The scientific factors,
including engineering design and feasibility, should be
considered in RMDM. These factors focus on technology
transfer (realistic performance of the technology), duration
of protection, and FS data uncertainties. These factors will
influence the decision whether or not to proceed with
selection of a particular remedy. They are detailed below:
Technology Transfer.
This factor concerns the
treatability of the contaminated debris or media by a
preferred technology or early action. Although the
recommended technology may appear attractive, a number
of problems must be overcome before actual selection or
implementation of the action. The following are a few
examples:
&
Scale up.
&
Downtime and maintenance (including supplies).
&
Ownership/control.
&
Throughput to meet the required completion schedule.
&
Skills required or training requirements.
&
QLs and DLs.
&
Space requirements for the remediation process and
management of remediation wastes.
Duration of Protection. This factor concerns the duration
of the removal or remedial technology designed to treat or
address site risk. This factor is particularly important for
site radionuclides or non-aqueous phase liquid compounds
in the aquifer. The maintenance or replacement of barriers
or equipment is also a primary
6-16
concern for this factor. Although a technology or
alternative is effective, its effectiveness may not last long if
there is no source control or contamination from off-site
sources is not controlled
Data Uncertainty. This factor considers reliability and
uncertainty of certain site or FS data for use in selecting a
remedy, or for determining whether NFA is appropriate.
Uncertainty in the following data may also impact the risk
analyses or BRA results:
&
Adequacy of bench-scale or pilot-scale treatability
data.
&
Data uncertainties (volume,
geology/hydrogeology).
&
Field data and modeling data.
&
Overall uncertainty of the source of site contamination.
matrices,
site
6.2.4.2 Non-Scientific Factors. Non-scientific factors
should also be considered in RMDM because some of these
factors are key to a successful site remediation. Most of
these factors are internal, but can also be external.
Examples of these factors are enforcement, compliance,
schedule, budget, competing risk reduction priorities,
community inputs, and societal/economic value of the
resources to be protected. These factors will influence the
decision on whether or not certain removal or RAs should
be taken, or on which remedies are to be selected. These
factors are detailed below.
Enforcement and Compliance. Certain courses of action
(including risk management decisions) have been agreed
upon early in the process and have been incorporated in the
IAG or FFA. This is particularly germane to some earlier
HTRW sites. Nonetheless, the requirements specified in
the enforcement documents or administrative order of
consent, IAG, FFA should be followed by the risk manager
or PM with few exceptions. When risk-related factors or
other non-risk factors are over-arching, the risk manager
should then raise this issue to higher echelon or to the legal
department for further action or negotiation.
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Competing Risk Reduction Priorities. Although related
to risk, this factor represents the competing interest among
programs or within the project for a limited source of
funding to perform risk reduction activities. Since it is
likely that not all sites will be cleaned up at an equal pace,
the planning and execution of environmental restoration
among these units should follow a prioritization scheme.
However, the scheme developed according to risk may not
be the same according to the customer, the base
commander, or the agencies. The risk manager or PM must
seek common ground to resolve this issue so that resources
can be expended to produce incremental environmental
benefits.
Schedule and Budget. These factors usually go together
because the more protracted the project life, the more
resources the project will demand. While each PM would
like to comply with risk-based considerations with little
margin of error, the PM may have no choice but to make
risk management decisions with larger uncertainties than he
or she would prefer, due to schedule and budget
constraints.
Community Input. Opportunity for the stakeholders or
community to provide input into the permit modification is
provided when primary documents are prepared, i.e., RFI
Work Plan, RFI/CMS reports, the proposed remedies, and
the CMI Work Plan. Superfund also provides similar
opportunities for public participation. To be successful in
site remediation and closeout, the risk managers must be
able to communicate risks effectively in plain and clear
language without bias. Early planning and solicitation of
community input is essential to democratization of RMDM.
Some of the following issues may be of concern to the
communities:
&
Ineffective communication of risks and uncertainties.
&
Lack of action (some action is preferred to no action).
&
Not in my backyard (off-site transportation of
contaminated soil, debris or sediment should avoid
residential neighborhoods).
&
Any treatment effluent or discharge is unacceptable
(on-site incineration is seldom a preferred option
except for mobile incinerators, in certain instances).
&
The remedy should not impede economic growth or
diminish current economic and recreational value of
resources to be protected.
&
Cleanup will improve the quality of life and increase
property values or restoration of recreational or
economic resources.
Societal/Economic Value of the Resources to be
Protected. This non-risk factor concerns the community
sentiment on how fast or in what manner the resources
impacted by site contaminants should be restored. These
resources may include surface water bodies, wildlife, and
game animals. Most communities would like to see
impacted resources restored to original use, however, this
can be difficult to achieve. Some communities may be
willing to accept natural attenuation or no action options for
impacted surface water bodies, given the opportunity to
examine the pros and cons of all options. Therefore, it is
recommended that the risk manager execute a community
relations plan in earnest in order to solicit the citizens' input
on the risk reduction approach and issues of concern. Key
community spokespersons may also be appointed to the site
action committee to facilitate such dialogue and
communication.
6.2.4.3 A Balanced Approach. In conclusion, the risk
manager should consider all risk and non-risk criteria
before making risk management site decisions. Due to
uncertainties associated with risk assessment or analysis,
the decision-maker must review risk findings and the
underlying uncertainties, and consider other non-risk
factors in the overall risk management equation. When
making risk management decisions, the risk manager
should keep an open mind regarding the approaches to
meet the project objective. In order to make informed site
decisions, the risk assessor must present risk estimates in
an unbiased manner. With an understanding of the volume
of contaminants of concern, significance and relevance of
the effects and potentially impacted receptors, fate/transport
properties of the COCs, and completeness of the exposure
pathways, the risk manager, PM, and stakeholders will be
better equipped to make informed decisions. These
decisions should be consistent with the overall site strategy,
which is developed early in the project planning phase, and
which may evolve throughout the project.
6-17
EM 200-1-4
31 Jan 99
6.3 DESIGN CONSIDERATIONS
Risk assessment methodology can be an important tool in
the design phase of CERCLA RAs or RCRA corrective
measure implementation. During the early phase of
RD/RA or CMI, risk assessment results can help
determine: 1) whether the selected remedy can be
implemented without posing an unacceptable short-term
risk or residual risk; and 2) control measures (operational
or engineering) to mitigate site risks and to assure
compliance with ARARs, TBC requirements, and permit
conditions. The risk and safety hazard information will be
evaluated by the site decision-makers, along with
information concerning design criteria, performance goals,
monitoring/compliance requirements prior to making risk
management decisions regarding the above questions.
Further, the decision-makers consider potential
requirements such as ARARs and TBCs in determining
design changes or control measures.
&
Neutralization or chemical deactivation of effluent
(continuous process or batch).
&
Use of remote control vehicle for handling, opening, or
cutting of drums containing explosive or highly
reactive or toxic substances.
6.3.1.1 Operational Control.
Where appropriate,
administrative control measures (procedural and
operational) safeguards should be recommended by the
PM, design engineer, or field supervisor during RA, with
inputs from the risk assessor and other relevant technical
and compliance specialists. Examples of these control
measures include:
&
Establish short-term trigger levels which will require
work stoppage or upgrade of the remediation
procedures (e.g., dredging of toxic sediments). Either
biological or chemical indicators, or their combination
could be used as the trigger levels. These levels
should be developed in the RD/RA or CMI project
phase by the risk assessor and other technical
specialists, including the modeler.
&
Consistent with the above trigger or acute concern
levels, evaluate on-site performance with field
equipment to assure adequate remediation.
Engineering Control - Where appropriate (when shortterm risks are determined to be unacceptable), engineering
controls should be recommended by the design engineer
with inputs from the risk assessor, ecologist, compliance
specialist, and the air modeler. Examples of these control
measures include:
&
Afford the proper protection of sensitive environments
by careful planning and positioning of staging area,
storage or management of remediation wastes,
selection of equipment with low load bearing, and
season or time period when the remediation should be
completed.
&
VOC and Semi-Volatile Organic Compounds (SVOC)
emissions - activated carbon canisters, after burners,
or flaring, prior to venting.
&
Establish a zone of decontamination and proper
management of effluent or waste generated from this
zone.
&
Metals and SVOC airborne particles - wetting of work
areas; particulate filter/bag house, wet scrubber, or
electrostatic precipitator (for thermal treatment
devices or incinerators).
&
Secure and control access to areas where RAs are
being implemented at all time.
This section addresses the above issues, i.e., risk
management considerations in RD, compliance with
ARARs, including the CAA, CWA, ESA, and other major
environmental statutes, and control measures required to
mitigate risks.
6.3.1
&
Potential Risk Mitigation Measures.
Fugitive emissions - monitoring of valves, pipe joints,
and vessel openings; and barrier/enclosure of work
areas (e.g., a can or shield over the auger stem).
6-18
6.3.1.2 Institutional Control. Institutional controls are
particularly pertinent for remedies which involve
containment, on-site disposal of wastes, or wetlands
remediation. Institutional controls should be recommended
by the customer, PM, and other site decision-makers.
Examples of these control measures include:
EM 200-1-4
31 Jan 99
&
Recording land use restrictions in the deeds (deed
restrictions) for future use of certain parcels or areas
where hazardous substances or wastes are contained.
&
Erection of placards, labels, and markers which
communicate areas where human exposure may pose
short-term or residual risks.
discharges could be a permitted activity. Nonetheless, this
issue has to be resolved if the RAOs are risk-based and do
not consider off-site influences or contribution to the
contaminants requiring remediation. Off-site source
control and containment, waste minimization, and closure
issues should be raised by the risk manager to the agencies,
USACE customers, and higher echelon.
&
Security fences and barriers.
&
BRAC. With BRAC, the land use of closed defense
facilities may not be indefinitely controlled and the
legislation governing BRAC holds the U.S.
government responsible for future cleanup of
contamination caused by government activities.
Cleanup criteria and long-term remedies should take
land use into consideration for implementation of an
effective site closeout strategy.
For example,
conversion of a military base into a state park or refuge
area will require different cleanup objectives than
cleanup
to
the
level
acceptable
for
industrial/commercial usage. This issue should be
addressed early in the site strategy development phase
with input from customers, local re-development
commissions, state, and other stakeholders.
&
Verification of cleanup. The risk management
decision concerning verification of cleanup, i.e., the
numerical value of the RAO, should be based on a
combination of factors: risk, uncertainty, statistics,
analytical DLs/matrices, and costs. Although RAOs
have been negotiated or determined in the ROD, the
sampling method and statistical requirements must be
clearly articulated before design and implementation
of the corrective measures or remedial alternatives.
6.3.2
Risk Management; Degree of Protectiveness.
Not only should a selected RA (corrective measure) be able
to meet balancing criteria, the RA must be protective, i.e.,
in terms of reducing site risks. In designing a selected
remedy, the site decision-makers may face operational or
engineering issues which are likely to require risk
management decisions. For example, if a detailed analysis
of a selected remedy reveals potential short-term or residual
risks, the decision-makers must decide to what extent and
with what control measures are necessary to abate the risk.
Inputs from the risk assessor will be needed to help make
informed risk management decisions. The following are
examples of key risk management considerations for
designing an effective remediation strategy:
&
Acceptability of control measures. There are
potential operational (procedural) or engineering
control measures to address the short-term risks. The
risk assessor, in coordination with the design engineer,
expert ecologist(s)/advisory panel, and other project
team members, assesses the effectiveness of any
proposed control measures.
&
Removal of control measures. Before a control
measure is implemented, the decision on the minimum
performance and when to stop requiring the control
measure has to be addressed. This is particularly
important if control measures are costly to implement
and maintain.
&
Effectiveness of the remediation. Remediation
should effectively address on-site contamination if
there is an continuing off-site (regional) source. This
consideration is particularly important for ground
water and sediment contamination remediation. This
regional source control strategy should not be
confused with the identification of Potentially
Responsible Parties since some of the
Risk management decisions during the design phase of a
CERCLA or RCRA remediation should be flexible,
considering the uncertainty in the risk assessment results,
acceptable risk range, confidence level of toxicity data or
criteria to support the assessment, engineering feasibility,
reliability of the measures (operational changes vs.
pollution control equipment), state and community
acceptance, and cost. It is recommended that risk managers
and site decision-makers request input from all members of
the project team for pros and cons of proposed control
measures to address the short-term risks.
6-19
EM 200-1-4
31 Jan 99
APPENDIX A
REFERENCES
DOD, 1994b. Relative Risk Site Evaluation Primer.
Interim Edition. Washington, D.C.
A.1 REQUIRED PUBLICATIONS.
References listed below have been cited in the text.
U.S. Army (USA), 1991 (February). Department of the
Army Pamphlet (DA Pam) 40-578. Health Risk
Assessment Guidance for Installation Restoration
Program and Formerly Used Defense Sites.
Executive Order (EO) 11990 (Presidential Document),
1977 (May). Protection of Wetlands.
EO 12088. October 13, 1978. Federal Compliance with
Pollution Control Standards. 43 FR 47707.
EO 12498. January 8, 1985.
Process. 50 FR 1036.
Regulatory Planning
EO 12580.
January 29,
Implementation. 52 FR 2923.
1987.
USA. Army Regulation (AR) 200-1. Environmental
Protection and Enhancement.
U.S. Army Corps of Engineers (USACE). EM 200-1-1.
Validation of Analytical Chemistry Laboratories.
USACE. EM 200-1-2. Technical Project Planning (TPP)
Process.
Superfund
EO 12777, 1991. Implementation of Section 311 of the
Federal Water Pollution Control Act of October 18, 1972
and the Oil Pollution Act of 1990.
U.S. Department of Defense (DOD), 1973 (May).
Directive 5100.50. Protection and Enhancement of
Environmental Quality.
DOD, 1977a. Directive 5030.41. Oil and Hazardous
Substances Pollution Prevention and Contingency
Program.
DOD, 1977b (August).
Directive 4120.14.
Environmental Pollution, Prevention, Control, and
Abatement.
DOD, 1978. Directive 6230.1. Safe Drinking Water.
DOD, 1979 (July). Directive 6050.1. Environmental
Effects in the United States of Department of Defense
Actions.
DOD, 1993. Memorandum from the Deputy Secretary of
Defense to Addressees; Subj: Fast Track Cleanup at
Closing Installations. Washington, D.C. September 9.
DOD, 1994a. Memorandum from the Deputy Secretary of
Defense to Addressees; Subj: Fast Track Cleanup Finding of Suitability to Transfer (FOST) for BRAC
Property. Washington, D.C.
USACE. EM 200-1-3. Requirements for the Preparation
of Sampling and Analysis Plans.
USACE. EM 200-1-4. Risk Assessment Handbook:
Volume II - Environmental Evaluation.
USACE. EM 200-1-6. Chemical Quality Assurance for
HTRW Projects.
USACE, 1996a (January 17).
Management Plan.
USACE HTRW
USACE, 1992. Environmental Compliance Assessment
System (ECAS) Assessment Protocols. Construction
Engineering Research Laboratories (CECER).
U.S. Environmental Protection Agency (USEPA), 1985
(Feb). EPA/600/8-85/002. Rapid Assessment of
Exposure to Particulate Emissions from Surface
Contamination Sites.
USEPA, 1986. EPA/530-SW-86-053. RCRA Facility
Assessment Guidance. Office of Solid Waste/Waste
Management Division.
USEPA, 1987a (July). EPA/600/8-87/042. Selection
Criteria for Mathematical Models Used in Exposure
Assessments: Surface Water Models.
USEPA 1987b (July). EPA/530/SW-87/017. Alternate
Concentration Limit Guidance, Part 1. ACL Policy and
A-1
EM 200-1-4
31 Jan 99
Information Requirements. Office of Solid Waste/Waste
Management Division.
USEPA, 1988a. EPA/530-SW-88-028. RCRA Corrective
Action Plan.
USEPA, 1988b. Enforcement Actions under RCRA and
CERCLA at Federal Facilities.
USEPA, 1988c. Evaluation Process for Achieving
Federal Facility Compliance.
USEPA, 1988d (April). EPA/540/1-88/001. OSWER
Directive 9285.5-1. Superfund Exposure Assessment
Manual. Office of Emergency and Remedial Response.
USEPA, 1988e (May). EPA/600/8-88/075. Selection
Criteria for Mathematical Models Used in Exposure
Assessments: Ground-Water Models.
USEPA, 1988f (May). EPA/530/SW-87/017. Alternate
Concentration Limit Guidance Based on 264.94(b)
Criteria Case Studies. Office of Solid Waste/Waste
Management Division.
USEPA, 1988g (June). EPA/530-SW-88-029. RCRA
Corrective Action Interim Measures Guidance. Interim
Final. Office of Solid Waste and Emergency Response.
USEPA, 1988h (September). EPA-450/4-88-009. A
Workbook of Screening Techniques for Assessing Impacts
of Toxic Air Pollutants.
USEPA, 1988i (October). EPA/540/G-89/004. OSWER
Directive 9355.3-01. Guidance for Conducting Remedial
Investigations and Feasibility Studies Under CERCLA.
Office of Emergency and Remedial Response.
USEPA, 1988j (November).
Federal Facilities
Compliance Strategy. Office of Federal Activities, Office
of External Affairs.
USEPA, 1989a (January).
EPA-450/1-89-003.
Air/Superfund National Technical Guidance Study Series:
Volume III - Estimation of Air Emissions from Cleanup
Activities at Superfund Sites. Office of Air Quality
Planning and Standards.
A-2
USEPA, 1989b (March). EPA/540/1-89/002. Risk
Assessment Guidance for Superfund, Volume I (RAGS):
Human Health Evaluation Manual. Interim Final. Office
of Emergency and Remedial Response.
USEPA, 1989c (March). EPA/600/3-89/013. Ecological
Assessment of Hazardous Waste Sites: A Field and
Laboratory Reference.
Office of Research and
Development.
USEPA, 1989d (March). EPA/625/3-89/-16. Interim
Procedures for Estimating Risks Associated with
Exposures to Mixtures of Chlorinated Dibenzo-p-Dioxins
and -Dibenzofurans (CDDs and CDFs) and 1989 Update.
USEPA, 1989e (17 April). EPA Order 5360.1. Policy
and Program Requirements to Implement the Quality
Assurance Program. Office of the Administrator.
USEPA, 1989f (May). RCRA Facility Investigation (RFI)
Guidance. Vol. I. Interim Final. Office of Solid Waste,
EPA.
USEPA, 1989g (August). EPA/540/G-89/006. CERCLA
Compliance With Other Laws Manual - Draft Guidance.
Office of Emergency and Remedial Response.
USEPA, 1989h (August). EPA/540/G-89/009. OSWER
Directive 9234.1-02. CERCLA Compliance With Other
Laws Manual - Part II. Office of Emergency and Remedial
Response.
USEPA, 1989i (August). Federal Facilities Negotiation
Policy. Office of Emergency and Remedial Response.
OSWER Directive 9992.3.
USEPA, 1989j (December). EPA/540/1-89/002. Risk
Assessment Guidance for Superfund: Vol. 1 - Human
Health Evaluation Manual (Part A). Office of Emergency
and Remedial Response.
USEPA, 1990a (January). OSWER Directive 9992.4.
Federal Facilities Hazardous Waste Compliance Manual.
Office of Waste Programs Enforcement.
EM 200-1-4
31 Jan 99
USEPA, 1990b (January).
EPA/600/6-90/003.
Methodology for Assessing Health Risks Associated with
Indirect Exposure to Combustor Emissions.
USEPA, 1990c (May). National Oil and Hazardous
Substances Pollution Contingency Plan. Final Rule.
Office of Solid Waste and Emergency Response. 55 FR
8660.
USEPA, 1990d (July). Corrective Action for Solid Waste
Management Units at Hazardous Waste Management
Facilities. Proposed Rule. Office of Solid Waste. 55 FR
30798.
USEPA, 1990e (August). EPA-450/1-89-002a.
Air/Superfund National Technical Guidance Study Series:
Volume II - Estimation of Baseline Air Emissions at
Superfund Sites. Office of Air Quality Planning and
Standards.
USEPA, 1990f (September).
EPA/540/8-89/014.
Superfund Emergency Response Actions - a Summary of
Federally Funded Removals, Fourth Annual Report,
Fiscal Year 1989. Office of Research and Development.
USEPA, 1991a. OSWER Directive 9355.0-30. Role of
the Baseline Risk Assessment in Superfund Remedy
Selection Decisions. Memorandum from Don R. Clay, the
Assistant Administrator to Regional Division Directors.
USEPA, 1991b (March). Timothy Fields, Jr. Memo,
OSWER Directive 9285.6-03. Human Health Evaluation
Manual, Supplemental Guidance: “Standard Default
Exposure Factors.”
Evaluation of Remedial Alternatives”.
Emergency and Remedial Response.
Office of
USEPA, 1992a. Hazard Ranking System Guidance.
Interim Final.
USEPA, 1992b. EPA-450/1-92-004. Estimation of Air
Impacts for the Excavation of Contaminated Soil.
USEPA, 1992c (January). EPA/600/8-91/011B. Dermal
Exposure Assessment: Principles and Applications. Office
of Health and Environmental Assessment.
USEPA, 1992d (February 26). Guidance on Risk
Characterization for Risk Managers and Risk Assessors.
Memorandum from F. Henry Habicht, Deputy
Administrator.
USEPA, 1992e (March). OERR 9200.6-303. Health
Effects Assessment Summary Tables; Annual FY 92.
Environmental Criteria and Assessment Office. Prepared
for Office of Emergency and Remedial Response.
USEPA, 1992f (March). EPA/600/R-92/047. Reference
Guide to Odor thresholds for Hazardous Air Pollutants
Listed in the Clean Air Act Amendments of 1990.
USEPA, 1992g (April 7). OSWER Directive 9203.1-01.
Superfund Accelerated Cleanup Model (SACM). Office
of Solid Waste and Emergency Response. (Also see
OSWER Directive 9203-1-03, July 7, 1992, Guidance on
the Implementation of the SACM under CERCLA).
USEPA, 1992h (April). OSWER Directive 9285.7-09A.
Guidance for Data Useability in Risk Assessment (Part A).
Final report. Office of Emergency and Remedial Response.
USEPA, 1991c (September). OSWER Directive 9345.001A. Guidance for Performing Preliminary Assessments
Under CERCLA. Hazardous Site Evaluation Division,
Office of Emergency and Remedial Response.
USEPA, 1992i (May 29). Guidelines for Exposure
Assessment. 57 FR 22888.
USEPA, 1991d (December). OSWER Directive 9285.701B. Human Health Evaluation Manual, Part B:
“Development of Risk-Based Preliminary Remediation
Goals. Office of Emergency and Remedial Response.
USEPA, 1992j (May). OSWER Directive 9285.7-081.
Supplemental Guidance to RAGS: Calculating the
Concentration Term.
Office of Solid Waste and
Emergency Response.
USEPA, 1991e (December). OSWER Directive 9285.701C. Human Health Evaluation Manual, Part C: “Risk
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PB92-963362. Guidance for Data Useability in Risk
Assessment. Part B.
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USEPA, 1992l (September). OSWER Directive 9234.222FS. ARARs Fact Sheet - Compliance With Clean Air
Acts and Associated Air Quality Requirements. Office of
Emergency and Remedial Response.
USEPA, 1992m (September). OSWER Directive
9345.0-05. Guidance for Performing Site Inspections
Under CERCLA. Office of Emergency and Remedial
Response.
USEPA, 1992n (October). EPA/625/R-92/014. RCRA
Corrective Action Stabilization Technologies Proceedings. Office of Research and Development.
USEPA, 1992o (November). EPA-450/1-89-001a.
Air/Superfund National Technical Guidance Study Series:
Volume I - Overview of Air Pathway Assessments for
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and Standards.
USEPA, 1993a (February 16). Corrective Action
Management Units and Temporary Units; Corrective
Action Provisions; Final Rule. Office of Solid Waste. 58
FR 8658.
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Aromatic Hydrocarbons, Final Draft.
USEPA, 1993c (May).
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A-4
Sites and RCRA Corrective Action Facilities. Office of
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USEPA, 1995b (February).
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Screening Guidance: Technical Background Document.
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Soil
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Technical Review Workgroup for Lead for an Interim
Approach to Assessing Risks Associated with Adult
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USEPA, 1997a (March). EPA/630/R-97/001. Guiding
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A.2 RELATED PUBLICATIONS.
The following list represents additional sources of
information related to this manual.
U.S. Army Environmental Hygiene Agency
(USAEHA), 1992 (January).
TG No. 185.
Commander's Guide to the Health Risk Assessment
Process.
U.S. Environmental Protection Agency (USEPA), 1983
(November). EPA/600/8-83/030. Rapid Assessment of
Potential
Ground-Water Contamination Under
Emergency Response Conditions. Office of Health and
Environmental Assessment.
USEPA, 1985 (August). EPA/560/5-85/026. Verification
of PCB Spill Cleanup by Sampling and Analysis. Office
of Toxic Substances.
USEPA, 1986 (June). OSWER Directive 9355.0-4A.
Superfund Remedial Design and Remedial Action
Guidance. Office of Emergency and Remedial Response.
USEPA, 1986 (May). EPA/560/5-86. Field Manual for
Grid Sampling of PCB Spill Sites to Verify Cleanup.
Office of Toxic Substances.
USEPA, 1986 (24 September).
Guidelines for
Carcinogen Risk Assessment. Office of Health and
Environmental Assessment. 51 FR 33992.
A-5
EM 200-1-4
31 Jan 99
USEPA, 1986 (24 September). Guidelines for Health
Risk Assessment of Chemical Mixtures. Office of Health
and Environmental Assessment. 51 FR 34014.
USEPA, 1986 (November). Test Methods for Evaluating
Solid Waste. Office of Solid Waste and Emergency
Response. SW-846. Third Edition.
USEPA, 1986. Hazardous Waste Management Rule:
Final Organic Leachate Model (OLM). Office of Solid
Waste and Emergency Response. 51 FR 41100.
USEPA, 1986. EPA/600/6-86/002. NTIS#: PB86232774.
Development of Advisory Levels for
Polychlorinated Biphenyls (PCB) Cleanup. Office of
Health and Environmental Assessment.
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Data Quality Objectives for Remedial Response Activities:
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Soil Sampling Quality
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Analyses -- Multi-Media, Multi-Concentration. Office of
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EPA/540/2-89/057.
Determining Soil Response Action Levels Based on Potential Contaminant Migration to Groundwater: A
Compendium of Examples. Office of Emergency and
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USEPA, 1989 (October 21). Managing the Corrective
Action Program for Environmental Results: the RCRA
Facility Stabilization Effort; Memorandum from S.K.
Lowrance and B.M. Diamond to Regions I-X Waste
Management Division Directors. Office of Solid Waste
and Office of Waste Programs Enforcement.
USEPA, 1989 (December 12). EPA/530-SW-90-021.
Report on Minimum Criteria to Assure Data Quality.
Office of Solid Waste.
USEPA, 1989 (December 13). Guidance on Handling
and Reporting Chemical Concentration on Data in
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Support Section, EPA Region III.
USEPA, 1989. OSWER Directive #9355.4-02. Interim
Guidance on Establishing Soil Lead Cleanup Levels at
Superfund Sites. Office of Emergency and Remedial
Response.
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Federal Facilities Hazardous Waste Compliance Manual.
Office of Waste Programs Enforcement.
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Procedures. Interim Final. Office of Emergency and
Remedial Response.
USEPA, 1990 (May). EPA/600/4-90/013. A Rationale
for the Assessment of Errors in the Sampling of Soils.
Environmental Monitoring Systems Laboratory.
USEPA, 1990 (July 18). Hazardous Waste Management
Rule: EPA CML Landfill Attenuation Factors (DAFs).
Final Rule. Office of Solid Waste and Emergency
Response. 55 FR 32999.
USEPA, 1990 (July). Health Effects Assessment
Summary Tables and User's Guide. Environmental
Criteria and Assessment Office. Prepared for Office of
Emergency and Remedial Response.
USEPA, 1990 (August). OSWER Directive 9355.4-1.
Guidance on Remedial Actions for Superfund Sites with
PCB Contamination. Office of Emergency and Remedial
Response.
USEPA, 1990. EPA/530-SW-90-036. RCRA Orientation
Manual. 1990 Edition. Office of Solid Waste/Permits and
State Programs Division.
USEPA, 1991 (February).
EPA/540/P-91/001.
Conducting Remedial Investigation/Feasibility Studies for
CERCLA Municipal Landfill Sites. Office of Emergency
and Remedial Response.
USEPA, 1991 (24 April). Facsimile from John Wilson to
Peter Tong. Subject: Biodegradation Rate or Extent of
Removal of Chemicals in Pristine and Contaminated
Subsurface Materials. U.S. Environmental Protection
Agency, Office of Research and Development, Robert S.
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USEPA, 1991 (May 26). Implementing the Deputy
Administrator's Risk Characterization Memorandum.
Memorandum from Henry Longest and Bruce Diamond to
regional waste management division directors. Office of
Emergency and Remedial Response and Office of Waste
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USEPA, 1991 (July). EPA/625/6-90/016b. Handbook Ground Water, Vol. II: Methodology. Office of Research
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USEPA, 1991 (August).
EPA/625/6-91/026.
Stabilization Technologies for RCRA Corrective Actions.
Office of Research and Development.
USEPA, 1991 (November). Implementation Document
for Boiler and Industrial Furnace (BIF) Regulations.
Draft. Office of Solid Waste.
USEPA, 1991 (November). OSWER Directive 9360.4.
Removal Program Representative Sampling Guidance,
Volume 1 - Soil. Office of Emergency and Remedial
Response.
USEPA, 1992 (January).
EPA-450/1-92-002.
Air/Superfund National Technical Guidance Study Series:
Guideline for Predictive Baseline Emissions Estimation
Procedures for Superfund Sites. Office of Air Quality
Planning and Standards.
USEPA, 1992 (February 11). New Interim Region IV
Guidance. EPA Region IV.
USEPA, 1992 (February).
EPA-450/1-92-003.
Air/Superfund National Technical Guidance Study Series:
Screening Procedures for Estimating the Air Impacts of
Incineration at Superfund Sites. Office of Air Quality
Planning and Standards.
USEPA, 1992 (August). Intermittent Bulletin, Vol. 1, No.
1. SACM Program Management Update - Identifying
SACM Program Management Issues. Draft. Superfund
Revitalization Activity, Office of Emergency and Remedial
Response.
USEPA, 1992 (August).
Assessing Sites Under
Superfund Accelerated Cleanup Model - Quick Reference
Fact Sheet. Draft. Hazardous Site Evaluation Division,
Office of Emergency and Remedial Response.
USEPA, 1992 (September). EPA-451/R-92-002.
Air/Superfund National Technical Guidance Study Series:
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Assessing Potential Indoor Air Impacts for Superfund
Sites. Office of Air Quality Planning and Standards.
USEPA, 1992 (October). EPA/625/R-92/014. RCRA
Corrective Action Stabilization Technologies Proceedings. Office of Research and Development.
USEPA, 1992 (December 22). Water Quality Standards;
Establishment of Numeric Criteria for Priority Toxic
Pollutants; States' Compliance, Final Rule. Office of
Water. 57 FR 60848.
USEPA, 1993 (September). Data Quality Objectives
Process for Superfund. Interim Final Guidance. Office of
Emergency and Remedial Response.
USEPA, 1993 (April). Drinking Water Regulations and
Health Advisories. Office of Water.
USEPA. On-Line Database: Integrated Risk Information
System (IRIS).
American Conference of Governmental Industrial
Hygienists, Inc (ACGIH), 1986. Threshold Limit
Values (TLVs) for Chemical Substances and Physical
Agents and Biological Exposure Indices (BEIs).
Agency for Toxic Substances and Disease Registry
(ATSDR), 1989. TP-88/10. Toxicological Profile for
Chromium.
ATSDR, 1990. TP-88/17. Toxicological Profile for
Lead.
Bailiff, M.D., and K.E. Kelly, 1990 (April). Hexavalent
Chromium in Hazardous Waste Incinerator Facilities:
From Stack Emissions to Health Risks. Paper presented at
the American Waste Management Association International
Specialty Conference on Waste Combustion in Boilers and
Industrial Furnaces, Kansas City, MO; April 17-20, 1990.
Bennett, D., and P. Tong, 1988 (September). The Use
of Health/risk Assessment Information in CERCLA
Related Activities. Toxics Integration Branch, Office of
Emergency and Remedial Response, U.S. Environmental
Protection Agency.
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Information and Health Assessments.” Environmental
Permitting. Winter 1992/1993. pp. 55-62.
Calabrese, et al., 1989. “How Much Soil do Young
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Sludge-borne Heavy Metals and Toxic Organics on Soils,
Plants, and Animals, and Related Regulatory Guidelines.”
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of the Workshop on the International Transportation,
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Recommendations. Pan American Health Organization.
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Assessment of Chemicals in the Environment. Phase III:
Evaluation and Recommendation of Alternative
Approaches. Exposure Assessment Task Group.
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Environment. Phase II: Uncertainty Analyses of Existing
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A-9
EM 200-1-4
31 Jan 99
APPENDIX B
LIST OF ACRONYMS
Assistant Chief of Staff for Installation
Management
ACL
Alternate Concentration Limit
AOC
Area of Concern/Area of Contamination
AR
Army Regulation
ARARs
Applicable or Relevant and Appropriate
Requirements
ASA(I,L,E) Assistant Secretary of the Army for
Installations, Logistics, and the
Environment
ATSDR
Agency for Toxic Substances and Disease
Registry
DSMOA/CA Department of Defense and State
Memorandum of Agreement/
Cooperative Agreement Program
ACSIM
BES
BRA
BRAC
Biomedical Engineering Service
Baseline Risk Assessment
Base Realignment and Closure
CAA
CDD
CDF
CERCLA
Clean Air Act
Chlorinated dibenzo-p-dioxin
Chlorinated dibenzofuran
Comprehensive Environmental Response,
Compensation, and Liability Act
CERCLA Information System
Community Environmental Response
Facilitation Act
Corrective Measures Implementation
Corrective Measures Study
Chemical of Concern
Chemical of Potential Concern
Coastal Resource Coordinator
Coastal Resource Coordination Branch
Conceptual Site Model
Central Tendency
Clean Water Act
Center of Expertise
CERCLIS
CERFA
CMI
CMS
COC
COPC
CRC
CRCB
CSM
CT
CWA
CX
DA
DEP
DERA
DERP
DL
DOD
DOE
DON
DQO
Department of the Army
Director of Environmental Programs
Defense Environmental Restoration
Account
Defense Environmental Restoration
Program
Detection Limit
Department of Defense
U.S. Department of Energy
Department of the Navy
Data Quality Objective
ECAS
EM
EO
ERA
ESA
EU
Environmental Compliance
Assessment System
Engineering Evaluation and Cost
Analysis
Engineer Manual
Executive Order
Ecological Risk Assessment
Endangered Species Act
Exposure Unit
FFA
FOSL
FOST
FS
FUDS
FY
Federal Facility Agreement
Finding of Suitability to Lease
Finding of Suitability to Transfer
Feasibility Study
Formerly Used Defense Sites
Fiscal Year
HEA
HEAST
Health and Environmental Assessment
Health Effects Assessment Summary
Tables
Human Health Risk Assessment
Hazard Index
Hazard Quotient
Headquarters, U.S. Army Corps of
Engineers
Hazard Ranking System
Hazardous and Solid Waste
Amendments of 1984
Hazardous, Toxic, and Radioactive
Waste
EE/CA
HHRA
HI
HQ
HQUSACE
HRS
HSWA
HTRW
IAG
IDL
IEUBK
IRA
IRIS
IRP
Interagency Agreement
Instrument Detection Limit
Integraged Exposure Uptake and
Biokinetic Model
Interim Remedial Action
Integrated Risk Information System
Installation Restoration Program
MC
MCL
MCLG
MDL
Monte Carlo
Maximum Contaminant Level
Maximum Contaminant Level Goal
Method Detection Limit
NAPL
NAAQS
Non-Aqueous Phase Liquids
National Ambient Air Quality Standards
B-1
EM 200-1-4
31 Jan 99
National Academy of Sciences
National Oil and Hazardous Substances
Pollution Contingency Plan
No Further Action
National Oceanic and Atmospheric
Administration
Notice of Noncompliance
National Priorities List
National Research Council
National Technical Information Service
SDWA
SF
SI
SITE
OE
Ordnance and Explosives
OMB
Office of Management and Budget
OSWER Office of Solid Waste and Emergency Response
(USEPA)
OU
Operable Unit
TBC
TCDD
TCL
TEF
TPH
TPP
TSD
NAS
NCP
NFA
NOAA
NON
NPL
NRC
NTIS
PA
PAH
PbB
PCB
PM
POL
PQL
PRG
Preliminary Assessment
Polycyclic Aromatic Hydrocarbon
Blood Lead
Polychlorinated biphenyl
Project Manager
Petroleum, Oil, and Lubricants
Practical Quantitation Limit
Preliminary Remediation Goal
QA/QC
QL
Quality Assurance/Quality Control
Quantitation Limit
RA
RAGS I
RAO
RBC
RCRA
RD
RFA
RfC
RfD
RFI
RG
RI
RMDM
RME
ROD
RPM
Remedial Action
Risk Assessment Guidance for Superfund
Remedial Action Objective
Risk-Based Concentration
Resource Conservation and Recovery Act
Remedial Design
RCRA Facility Assessment
Reference Concentration
Reference Dose
RCRA Facility Investigation
Remediation Goal
Remedial Investigation
Risk Management Decision-Making
Reasonable Maximum Exposure
Record of Decision
Remedial Project Manager
SACM
SAP
SARA
Superfund Accelerated Cleanup Model
Sampling and Analysis Plan
Superfund Amendments and
Reauthorization Act of 1986
B-2
SOW
SQL
SWMU
SVOC
TARA
UCL
UF
USACE
USACHPPM
Safe Drinking Water Act
Slope Factor
Site Inspection
Superfund Innovative Technology
Evaluation
Statement/Scope of Work
Sample Quantitation Limit
Solid Waste Management Unit
Semi-Volatile Organic Compound
Technical Approach for Risk
Assessment
To-Be-Considered
Tetrachlorodibenzo-p-dioxin
Target Cleanup Levels
Toxicity Equivalence Factor
Total Petroleum Hydrocarbons
Technical Project Planning
Treatment, Storage, or Disposal
UST
Upper Confidence Limit
Uncertainty Factor
U.S. Army Corps of Engineers
U.S. Army Center for Health
Promotion and Preventive Medicine
U.S. Air Force
U.S. Environmental Protection
Agency
Underground Storage Tank
VOC
Volatile Organic Compound
USAF
USEPA
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