ASTM E2081-22

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2081 − 22
Standard Guide for
Risk-Based Corrective Action
This standard is issued under the fixed designation E2081; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This guide provides guidance for the development of a Risk-Based Corrective Action (RBCA)
program that integrates the sciences of ecological and human health risk-based decision making into
the corrective action process. The RBCA provides a flexible, technically defensible framework for
correctiveactionthatisapplicabletoawiderangeofsitesandchemical(s)ofconcern.Theframework
incorporates a tiered analytical approach, applying increasingly complex levels of data collection and
analysis as the user proceeds through the process. It provides a starting point for the integration of
multiple regulatory programs into a site-wide corrective action activity and a technically defensible
process for achieving “No FurtherAction.” The successful implementation of the RBCAframework
is dependent on an understanding by the user of the technical policy decisions that are critical to the
risk management process and the identification and determination of these technical policy decisions
prior to beginning the process (see 3.2.60). There are numerous technical policy decisions that must
be made to implement the RBCAprocess, for example, defining data quality objectives, determining
target risk levels and addressing resource protection. It is not the intent of this guide to define
appropriate technical policy decisions. The RBCA process is not intended to replace existing
regulatory programs, but rather to complement these programs. Regardless of whether a corrective
actionisspecificallygovernedbyaregulatoryprogram,theusershouldconsulttheregulatoryagency
requirements to identify the appropriate technical policy decisions prior to implementing the RBCA
process. The RBCA process encourages user-led initiatives and stakeholder involvement in both the
development of the technical policy decisions and the RBCAprogram. It recognizes the diversity of
sitesandprovidesappendixesforpossibleapplicationsandexamples.Theappendixesareprovidedfor
additionalinformationandarenotmandatorysectionsofthisstandardguide.ASTMstandardsarenot
federal or state regulations; they are consensus standards that can voluntarily be followed.
1. Scope activities to site-specific conditions and risks. The evaluations
and methods used in the RBCA process begin with simple
1.1 This is a guide for conducting risk-based corrective
analyses in Tier 1 and move to more complex evaluations in
action (RBCA) at chemical release sites based on protecting
either Tier 2 or Tier 3, as applicable. The process of gathering
human health and the environment. The RBCAis a consistent
and evaluating data is conducted in a scaled fashion.
decision-making process for the assessment and response to
Consequently, only the data that are necessary for a particular
chemical releases. Chemical release sites vary greatly in terms
tier’s decision-making are collected at that tier.
ofcomplexity,physicalandchemicalcharacteristics,andinthe
risk that they may pose to human health and the environment.
1.2 This guide describes an approach for risk-based correc-
The RBCA process recognizes this diversity by using a tiered tive action. It is intended to help direct and streamline the
approach that integrates site assessment and response actions
corrective action process and to complement but not to
withhumanhealthandecologicalriskassessmenttodetermine supersede federal, state and local regulations. It can be em-
the need for remedial action and to tailor corrective action
ployed at sites where corrective action is being conducted
includingsiteswheretheremaynotbearegulatoryframework
for corrective action, or where the user wishes to conduct
correctiveactionsuchassitesinvoluntarycleanupprogramsor
ThisguideisunderthejurisdictionofASTMCommitteeE50onEnvironmental
Assessment, Risk Management and CorrectiveAction and is the direct responsibil-
underBrownfieldsinitiatives.Inaddition,itcanalsobeusedas
ity of Subcommittee E50.04 on Corrective Action.
a unifying framework when several different agency programs
Current edition approved April 1, 2022. Published May 2022. Originally
affect the site. Furthermore, the user should be aware of the
approvedin1998.Lastpreviouseditionapprovedin2015asE2081-00(2015).DOI:
10.1520/E2081-22. federal, state and local corrective action programs that are
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2081 − 22
applicable for the site and, regardless of the program, federal, chosen actions are protective of human health and the envi-
stateandlocalagencyapprovalsmayberequiredtoimplement ronment. The following general sequence of events is pre-
the processes outlined in this guide. Finally, regardless of scribed in RBCA:
whether a corrective action is specifically governed by a
1.8.1 Performaninitialsiteassessmentanddevelopthefirst
regulatory program, the user should consult the regulatory
iteration of the site conceptual model (see Guides E1689 and
agency requirements to identify the appropriate technical
E3240 and ISO 21365:2019). If the information is sufficient to
policy decisions prior to implementing the RBCA process.
demonstrate that there are no complete or potentially complete
exposure pathways, then no further action is warranted,
1.3 Therearenumeroustechnicalpolicydecisionsthatmust
1.8.2 Evaluate the site (see definition of site 3.2.50) for
be made to implement the RBCA process, for example,
response actions (multiple sites at a single facility may require
defining data quality objectives, determining target risk levels,
different response actions and times),
specifying the appropriate statistics and sample sizes for
1.8.3 Implement a response action that is appropriate for
calculating exposure concentrations, selection of exposure
conditions found at the site during the site response action
assumptions, determining when and how to account for cumu-
evaluation,
lative risks and additive effects among chemical(s) of concern
1.8.4 Define data requirements, develop data quality
and addressing resource protection. It is not the intent of this
guidetodefineappropriatetechnicalpolicydecisions.Theuser objectives, and perform a site assessment for the Tier 1
evaluation if the site conceptual model indicates that the tiered
must identify the appropriate technical policy decisions.
evaluation is appropriate,
1.4 The general performance standard for this guide re-
1.8.5 Conductanexposurepathwayanalysistodetermineif
quires that:
relevant ecological receptors and habitats are present and if
1.4.1 Technical policy decisions be identified before begin-
complete and potentially complete exposure pathways are
ning the process,
present. If no relevant ecological receptors or habitats or
1.4.2 Data and information collected during the RBCA
complete and potentially complete exposure pathways exist,
process, including historical data as well as new data collected
then no further action for relevant ecological receptors and
during the site assessment, will be relevant to and of sufficient
habitats is warranted,
quantity and quality to answer the questions posed by and the
1.8.6 For potential human exposure pathways, identify the
decisions to be made in the RBCA process,
applicable Risk Based Screening Levels (RBSL) and for
1.4.3 Actions taken during the risk-based decision process
potentialecologicalexposurepathways,identifytheapplicable
will be protective of human health and the environment,
Relevant Ecological Screening Criteria (RESC). In addition,
1.4.4 Applicable federal, state and local regulations will be
identify any Other Relevant Measurable Criteria (ORMC), as
followed (for example, waste management requirements, applicable. Collectively these are the Tier 1 corrective action
ground water designations, worker protection) and,
goals for the site;
1.4.5 Remedial actions implemented will not result in 1.8.7 ComparesiteconditionstotheTier1correctiveaction
higher risk levels than existed before taking actions. goals determined to be applicable to the site;
1.8.8 If site conditions meet the corrective action goals for
1.5 ASTM standards are not federal or state regulations,
chemical(s) of concern then, no further action is warranted,
they are consensus standards that can voluntarily be followed.
1.8.9 If site conditions do not meet corrective action goals
1.6 The RBCAprocess is not limited to a particular class of
for chemical(s) of concern then, one or more of the following
compounds.ThisguideisintendedtobeacompaniontoGuide
actions is appropriate:
E1739, and does not supersede that document for petroleum
1.8.9.1 Further tier evaluation;
releases. If a release site contains a mixture of releases of
1.8.9.2 Implement interim remedial action;
petroleum and other chemicals, this guide should be followed.
1.8.9.3 Design and implement remedial action to achieve
1.7 The United States Environmental Protection Agency the corrective action goals.
(USEPA) has developed guidance for human health risk
1.8.10 Define Tier 2 data requirements, data quality
evaluation(seeAppendixX9forotherresources).Manyofthe
objectives, collect additional site-specific information and
components of this guidance have been integrated into the
update the site conceptual model, as necessary, if further tier
RBCA framework. The science of ecological evaluation and
evaluation is warranted,
theprocessbywhichthescienceisapplied,however,arenotas
1.8.11 Develop point(s) of demonstration andTier 2 correc-
welldefinedandagreeduponashumanhealthriskassessment.
tive action goals based on Site-Specific Target Levels (SSTL),
Therefore, the information provided in this guide for each tier
Site-Specific Ecological Criteria (SSEC) or ORMC, where
evaluation for relevant ecological receptors and habitats is
appropriate, for complete and potentially complete exposure
general. The user is referred to Appendix X5, which provides
pathways, including exposure pathways for which no RBSL,
additional information regarding the development of a RBCA
RESC or ORMC, as applicable, were determined;
framework for protection of ecological resources.
1.8.12 Compare site conditions to the Tier 2 corrective
action goals determined to be applicable to the site;
1.8 The decision process described in this guide integrates
exposure and risk assessment practices with site assessment 1.8.13 If site conditions meet corrective action goals for
activities and remedial action selection to ensure that the chemical(s) of concern, then no further action is warranted,
E2081 − 22
Ecology’s risk-based corrective action approach to PFAS as an example;
1.8.14 If site conditions do not meet corrective action goals
numerous other states including Alaska, California, Colorado, Maine,
for chemical(s) of concern then, one or more of the following
Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New
actions is appropriate:
York, Pennsylvania, Rhode Island, and Vermont have robust programs to
1.8.14.1 Further tier evaluation;
address releases of PFAS to the environment. The appendixes are
1.8.14.2 Implement interim remedial action; provided for additional information and are NOT included as
mandatory sections of this guide.
1.8.14.3 Design and implement remedial action to achieve
the corrective action goals. 1.11 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
1.8.15 Define Tier 3 data requirements, data quality objec-
tivesandcollectadditionalsite-specificinformationandupdate standard.
the site conceptual model, as necessary, if further tier evalua-
1.12 This international standard was developed in accor-
tion is warranted,
dance with internationally recognized principles on standard-
1.8.16 Developpoint(s)ofdemonstrationandTier3correc-
ization established in the Decision on Principles for the
tive action goals based on SSTL, SSEC, or ORMC, where
Development of International Standards, Guides and Recom-
appropriate;
mendations issued by the World Trade Organization Technical
1.8.17 Compare site conditions to the Tier 3 corrective
Barriers to Trade (TBT) Committee.
action goals,
1.8.18 If site conditions meet corrective action goals for 2. Referenced Documents
chemical(s) of concern, then no further action is warranted, 2
2.1 ASTM Standards:
1.8.19 If site conditions do not meet corrective action goals
D5447Guide for Application of a Numerical Groundwater
forchemical(s)ofconcern,thenoneofthefollowingactionsis
Flow Model to a Site-Specific Problem
appropriate:
D5490Guide for Comparing Groundwater Flow Model
1.8.19.1 Implement interim remedial action to facilitate
Simulations to Site-Specific Information
reassessment of the tier evaluation;
D5610GuideforDefiningInitialConditionsinGroundwater
1.8.19.2 Design and implement remedial action to achieve
Flow Modeling
the corrective action goals.
D5611Guide for Conducting a Sensitivity Analysis for a
1.8.20 Develop and implement a monitoring plan based on
Groundwater Flow Model Application
thecorrectiveactiongoalstovalidatetheassumptionsusedfor
D5612Guide for Quality Planning and Field Implementa-
the tier evaluation and to demonstrate effectiveness of the
tion of a Water Quality Measurement Program
remedial action, as applicable.
D5718Guide for Documenting a Groundwater Flow Model
Application (Withdrawn 2022)
1.9 For chemical release sites currently in corrective action,
D6235Practice for Expedited Site Characterization of Va-
the user should review information and data available for the
dose Zone and Groundwater Contamination at Hazardous
site and determine the most appropriate entry point into the
Waste Contaminated Sites
RBCA framework consistent with the general performance
E1527PracticeforEnvironmentalSiteAssessments:PhaseI
standards and sequence of events outlined in this guide.
Environmental Site Assessment Process
1.10 This Guide is Organized as Follows—Section 2 lists
E1689Guide for Developing Conceptual Site Models for
referenced documents, Section 3 defines terminology used in
Contaminated Sites
this guide, Section 4 describes the significance and use of this
E1739Guide for Risk-Based Corrective Action Applied at
guide, Section 5 is a summary of the tiered approach, and
Petroleum Release Sites
Section 6 presents the RBCA procedures in a step-by-step
E1903Practice for Environmental Site Assessments: Phase
process. Appendix X1 provides guidance on developing tech-
II Environmental Site Assessment Process
nical policy decisions and building a RBCAprogram, Appen-
E1943Guide for Remediation of Ground Water by Natural
dix X2 provides examples of chemical properties and effects
Attenuation at Petroleum Release Sites
data that may be useful for a RBCAevaluation, Appendix X3
E2091Guide for Use of Activity and Use Limitations,
provides EXAMPLE development of RBSL, Appendix X4
Including Institutional and Engineering Controls
describes the use of predictive modeling, Appendix X5 pro-
E2205/E2205MGuide for Risk-Based CorrectiveAction for
vides an outline of the process of the ecological evaluation,
Protection of Ecological Resources
Appendix X6 provides information about activity and use
E2531Guide for Development of Conceptual Site Models
limitations, Appendix X7 includes illustrative examples of the
and Remediation Strategies for Light Nonaqueous-Phase
application of the RBCA framework, Appendix X8 addresses
Liquids Released to the Subsurface
Per- and polyfluoroalkyl substances (PFAS). PFAS are syn-
E3163Guide for Selection and Application of Analytical
theticchemicalsthatdonotoccurnaturallyintheenvironment.
There are many different types of PFAS such as perfluorocar-
boxylic acids (for example, PFOA, sometimes called C8, and
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
PFNA) and perfluorosulfonates (for example, PFOS and
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
PFHxS), and Appendix X9 includes references that may be
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
helpful to the user.
The last approved version of this historical standard is referenced on
NOTE 1—Appendix X8 references the Washington Department of www.astm.org.
E2081 − 22
Methods and Procedures Used during Sediment Correc- to eliminate or minimize potential exposures to chemical(s) of
tive Action concern, or to prevent activities that could interfere with the
E3164Guide for Sediment Corrective Action – Monitoring effectiveness of a remedial action, to ensure maintenance of
E3240GuideforRisk-BasedCorrectiveActionforContami- siteconditionsthatmeetthecorrectivegoalsforchemical(s)of
nated Sediment Sites concern.
E3242Guide for Determination of Representative Sediment 3.2.1.1 Discussion—These legal or physical restrictions are
Background Concentrations
intended to prevent adverse impacts to receptors and relevant
E3248GuideforNAPLMobilityandMigrationinSediment ecological receptors and habitats that may be exposed to
–Conceptual Models for Emplacement and Advection
chemical(s) of concern. Activity and use limitations include
2.2 Other Referenced Documents bothengineeringandinstitutionalcontrols.(SeeGuideE2091.)
California Office of Environmental Health Hazard
3.2.2 additive effects—referstocombinednon-cancereffects
Assessment, Toxicity Criteria Database, https://
of chemical(s) of concern with the same mechanism of action
data.ca.gov/dataset/toxicity-criteria-database, May 2019
in a receptor.
CRC CARE 2018, Practitioner guide to risk-based
3.2.3 bio-availability—a measure of the chemical(s) of con-
assessment, remediation and management of PFAS site
cern in environmental media that is accessible to an organism
contamination, CRC CARE Technical Report no. 43,
for absorption.
CRC for Contamination Assessment and Remediation of
3.2.4 biodegradation—Natural plant, animal, or microbial
the Environment, Newcastle, Australia.
metabolism that results in the reduction of mass of a chemi-
ISO 21365:2019 Soil quality -- Conceptual site models for
cal(s) of concern.
potentially contaminated sites
Pubchem databases; pubchem.ncbi.nlm.nih.gov
3.2.5 chemical release—Any spill or leak or detection of
U.S.EPA,GuidanceonSystematicPlanningUsingtheData
concentrations of chemical(s) of concern in environmental
QualityObjectivesProcess,EPAQA/G-4,EPA/240/B-06-
media.
01, 2006.
3.2.6 chemical(s) of concern—The specific compounds and
U.S. EPA, Comptox Dashboard: https://comptox.epa.gov/
their breakdown products that are identified for evaluation in
dashboard
the RBCA process.
U.S. EPA, ECOTOX database; https://cfpub.epa.gov/
3.2.6.1 Discussion—Identification can be based on their
ecotox/index.cfm
historical and current use at a site, detected concentrations in
U.S. EPA, Recommendations from the EPA Groundwater
environmental media and their mobility, toxicity, and persis-
Task Force, EPA 500-R-07-001, December 2007
tenceintheenvironment.Becausechemical(s)ofconcernmay
Washington Department of Ecology. Per- and Polyfluoro-
be identified at many points in the RBCA process, including
alkyl Substances. Chemical Action Plan. Publication 21-
beforeanydeterminationthattheyposeanunacceptableriskto
04-048. November 2021.
human health or the environment, the term should not auto-
matically be construed to be associated with increased or
3. Terminology
unacceptable risk.
3.1 The reader should review the definitions presented here
3.2.7 corrective action—The sequence of actions that in-
prior to reviewing the guide, as many of the terms included in
clude site assessment and investigation, risk assessment, re-
this guide may have different meanings than the specific
sponse actions, interim remedial action, remedial action, op-
regulatory definitions within existing federal, state or local
erationandmaintenanceofequipment,monitoringofprogress,
programs.Thefollowingtermsarebeingdefinedtoreflecttheir
makingnofurtheractiondeterminationsandterminationofthe
specificuseinthisguide.Theusershouldnotassumethatthese
remedial action.
definitions replace existing regulatory definitions. Where the
definitionoruseofaterminthisguidediffersfromanexisting 3.2.8 corrective action goals—concentration or other nu-
regulatory definition or use, the user should address these
meric values, physical condition or remedial action perfor-
differences prior to proceeding with the RBCA process. mance criteria that demonstrate that no further action is
necessary to protect human health and the environment.
3.2 Definitions of Terms Specific to This Standard:
3.2.8.1 Discussion—For example, these goals may include
3.2.1 activity and use limitations—Legalorphysicalrestric-
one or a combination of RBSL, SSTL, RESC, SSEC and
tions or limitations on the use of, or access to, a site or facility
ORMC chosen for source area(s), point(s) of demonstration
and point(s) of exposure. The corrective action goals are
AvailablefromCRCCARE,NewcastleUniversityLPOPOBox18.Callaghan
specific to each Tier in the evaluation.
NSW 2308 https://www.crccare.com/publications/technical-reports
Available from International Organization for Standardization (ISO), ISO 3.2.9 cumulative risks—referstothecombinedcarcinogenic
Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
risks from all exposure pathways for all chemicals for a
Switzerland, https://www.iso.org.
receptor.
AvailablefromUnitedStatesEnvironmentalProtectionAgency(EPA),William
Jefferson Clinton Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460,
3.2.10 direct exposure pathways—An exposure pathway
http://www.epa.gov.
where the point of exposure is at the source, without a release
Available from Washington Department of Ecology, 300 Desmond Drive SE,
to any other medium and without an intermediate biological
Lacey, WA 98503 https://apps.ecology.wa.gov/publications/summarypages/
2104048.html transfer step.
E2081 − 22
3.2.11 ecological evaluation—Aprocess for organizing and 3.2.23 institutional controls—A legal or administrative re-
analyzing data, information, assumptions and uncertainties to strictionontheuseof,oraccesstoasiteorfacilitytoeliminate
evaluate the likelihood that adverse effects to relevant ecologi- orminimizepotentialexposuretoachemical(s)ofconcern(for
cal receptors or habitats may occur or are occurring as a result example, restrictive covenants, restrictive zoning).
of exposure to chemical(s) of concern.
3.2.24 interim remedial action—The course of action taken
3.2.12 engineering controls—Physical modifications to a
to reduce migration of a chemical(s) of concern in its vapor,
site or facility to reduce or eliminate the potential for exposure
dissolved, or liquid phase, or to reduce the concentration of a
to chemical(s) of concern (for example, slurry walls, capping,
chemical(s) of concern at a source area(s).
hydraulic controls for ground water, or point-of-use water
3.2.25 maximum contaminant level (MCL)—A standard for
treatment).
drinking water established by USEPAunder the Safe Drinking
3.2.13 exposure assessment—The determination or estima-
Water Act which is the maximum permissible level of a
tion (qualitative or quantitative) of the magnitude, frequency,
chemical(s) of concern in water which is delivered to any user
duration and route of exposure between a source area and a
of a public water supply.
receptor.
3.2.26 natural attenuation—The reduction in the concentra-
3.2.14 exposure pathway—The course a chemical of con-
tion(s) of chemicals of concern in environmental media due to
cern takes from the source area(s) to a receptor or relevant
naturallyoccurringphysical,chemicalandbiologicalprocesses
ecological receptor and habitat.
(for example, diffusion, dispersion, adsorption, chemical deg-
3.2.14.1 Discussion—An exposure pathway describes the
radation and biodegradation).
mechanism by which an individual or population is exposed to
3.2.27 non-aqueous phase liquids (NAPL)—Chemicals that
a chemical of concern originating from a site. Each exposure
are insoluble or only slightly soluble in water that exist as a
pathway includes a source or release from a source of a
separateliquidphaseinenvironmentalmedia.Theycanbeless
chemical of concern, a point of exposure, an exposure route
dense or more dense than water.
and the potential receptors or relevant ecological receptors and
habitats. If the exposure point is not at the source, a transport 3.2.28 other relevant measurable criteria (ORMC)—
or exposure medium, or both, (for example, air or water) are
Parameters used to define corrective action goals for chemi-
also included. cal(s) of concern.
3.2.28.1 Discussion—The ORMC are concentration values,
3.2.15 exposure route—The manner in which a chemical(s)
other numeric values, physical condition or performance cri-
of concern comes in contact with a receptor (for example,
teria other than RBSL, RESC, SSTL or SSEC. Examples of
ingestion, inhalation, dermal contact).
ORMC are regulatory standards, consensus criteria, aesthetic
3.2.16 exposure scenario—The description of the
criteria, and ground water protection criteria. Technical policy
circumstances, including site properties and chemical
decisionsregardingORMCmayexist,ormayneedtobemade
properties, or the potential circumstances under which a
todeterminetheappropriatevalues,conditionsorperformance
receptororarelevantecologicalreceptororhabitatcouldbein
criteria that are used for the corrective action goals.
contact with chemical(s) of concern;
3.2.29 petroleum—Includescrudeoiloranyfractionthereof
3.2.17 facility—The property containing the source of the
thatisliquidatstandardconditionsoftemperatureandpressure
chemical(s) of concern where a release has occurred.Afacility
(15.6°C and 10 340 kg/m absolute).
may include multiple sources and therefore, multiple sites.
3.2.29.1 Discussion—The term includes petroleum-based
3.2.18 guide—a series of options or instructions that do not
substances comprised of a complex blend of hydrocarbons
recommend a specific course of action.
derived from crude oil through processes of separation,
3.2.19 hazard index—The sum of two or more hazard
conversion, upgrading, and finishing, (for example, motor
quotients for chemical(s) of concern or multiple exposure
fuels, jet fuels, lubricants, petroleum solvents, used oils).
pathways to a particular receptor, or both.
3.2.30 point(s) of demonstration—A location(s) selected
3.2.20 hazard quotient—The ratio of the level of exposure
between the source area(s) and the potential point(s) of
of a chemical of concern over a specified time period to a
exposure where corrective action goals are met.
reference dose for that chemical of concern derived for a
3.2.31 point(s) of exposure—The point(s) at which an indi-
similar exposure period.
vidualorpopulationmaycomeincontactwithachemical(s)of
3.2.21 incremental carcinogenic risk levels—The potential
concern originating from a site.
for incremental human carcinogenic effects, over background
3.2.32 potentially complete exposure pathway—A situation
canceroccurrencelevels,duetoexposuretothechemical(s)of
with a reasonably likely chance of occurrence in which a
concern. This is the individual lifetime excess cancer risk.
receptor or relevant ecological receptor or habitat may become
3.2.22 indirect exposure pathways—An exposure pathway
directly or indirectly exposed to the chemical(s) of concern.
with at least one intermediate release to any media, or an
intermediate biological transfer step, between the source and 3.2.33 practice—a definitive procedure for performing one
the point(s) of exposure (for example, chemical(s) of concern or more specific operations or functions that does not produce
from soil through ground water to the point(s) of exposure). a test result.
E2081 − 22
3.2.34 probabilistic evaluation—A modeling procedure concentrations, biological measures or other relevant generic
used to evaluate the uncertainty surrounding a probability criteria consistent with the technical policy decisions.
distribution when the result depends on a number of factors,
3.2.43 remedial action—Activities conducted to reduce or
each of which has its own variability and uncertainty.
eliminate current or potential future exposures to receptors or
3.2.35 qualitative ecological screening evaluation—A pro-
relevant ecological receptors and habitats.
cessconductedaspartoftheTier1evaluationwhereinrelevant
3.2.43.1 Discussion—These activities include monitoring,
ecological receptors and habitats and exposure pathways are
implementing activity and use limitations and designing and
identified.
operatingclean-upequipment.Remedialactionincludesactivi-
3.2.35.1 Discussion—Thenecessaryinformationcanbecol-
ties that are conducted to reduce sources of exposures to meet
lected as part of the data gathering activities during the initial
corrective action goals, or sever exposure pathways to meet
site assessment or theTier 1 site assessment ( 6.3.2 and 6.5.1).
corrective action goals.
Within Tier 1, this screening-level information, which is
3.2.44 response action—An immediate course of action,
typically qualitative, may be used to evaluate potential expo-
including monitoring, abatement or containment measures to
surepathwaystorelevantecologicalreceptorsandhabitatsand
mitigate known or potential hazards to human health, safety
to identify potential chemical(s) of concern. If available,
and the environment, taken before interim remedial action or
generic, non-site-specific ecological criteria and guidelines
remedial action.
(3.2.42) may be used to further evaluate complete and poten-
3.2.45 response action evaluation—Aqualitativeanalysisof
tially complete exposure pathways.
a site, based on known or readily available information, to
3.2.36 qualitative risk analysis—Anon-quantitative evalua-
identify the need for and urgency of response actions and the
tion of the potential risks at a site as determined by the
need for further information gathering. The analysis is also
potential exposure pathways and receptors based on known or
used to identify appropriate early risk reduction steps.
reasonably available information.
3.2.46 risk—The potential for, or probability of, an adverse
3.2.37 reasonable maximum exposure (RME)—The highest
effect. These may be expressed qualitatively or quantitatively.
exposure that is reasonably expected to occur at a site. RME’s
3.2.47 risk assessment—An analysis of the potential for
are estimated for individual exposure pathways or a combina-
adverse effects on receptors and relevant ecological receptors
tion of exposure pathways.
and habitats caused by a chemical(s) of concern from a site.
3.2.38 reasonably anticipated future use—Future use of a
3.2.47.1 Discussion—The risk assessment activities are the
site or facility which can be predicted with a reasonably high
basis for the development of corrective action goals and
degree of certainty given historical use, current use, and local
determination of where interim remedial actions, remedial
government planning and zoning.
action or a combination of actions are required.
3.2.39 receptors—The persons that are or may be affected
3.2.48 risk reduction—The lowering or elimination of the
by a release. (see relevant ecological receptors and habitats,
level of risk posed to human health or the environment
3.2.41, for non-human receptor definition).
through, response actions, interim remedial actions, remedial
3.2.40 reference dose—A toxicity value for evaluating po-
action or a combination of actions.
tential non-carcinogenic effects in humans resulting from
3.2.49 risk-based screening level/screening levels (RBSL)—
exposure to a chemical(s) of concern.
Non-site-specific human health risk-based values for chemi-
3.2.41 relevant ecological receptors and habitats—The
cal(s) of concern that are protective of human health for
ecological resources that are valued at the site.
specified exposure pathways utilized during the Tier 1 evalu-
3.2.41.1 Discussion—Because of the variety of ecological
ation.
resources that may be present, focusing upon those relevant to
3.2.50 site—The area(s) defined by the likely physical
a site is an important part of the problem formulation phase of
distribution of the chemical(s) of concern from a source area.
ecological evaluation. Identification of relevant ecological
3.2.50.1 Discussion—A site could be an entire property or
receptors and habitats is dependent upon site-specific factors
facility, a defined area or portion of a facility or property or
and technical policy decisions. Examples may include species
multiple facilities or properties. One facility may contain
or communities afforded special protection by law or regula-
multiple sites. Multiple sites at one facility may be addressed
tion; recreationally, commercially or culturally important re-
individually or as a group.
sources; regionally or nationally rare communities; communi-
ties with high aesthetic quality; and habitats, species or
3.2.51 site assessment—Acharacterization of a site through
communitiesthatareimportantinmaintainingtheintegrityand
an evaluation of its physical and environmental context (for
bio-diversity of the environment.
example, subsurface geology, soil properties and structures,
hydrology,andsurfacecharacteristics)todetermineifarelease
3.2.42 relevant ecological screening criteria (RESC)—
Generic, non-site specific ecological criteria or guidelines that has occurred, the levels of the chemical(s) of concern in
environmentalmedia,andthelikelyphysicaldistributionofthe
aredeterminedtobeapplicabletorelevantecologicalreceptors
and habitats, exposure pathways and site conditions utilized chemical(s) of concern.
during the Tier 1 evaluation.
3.2.51.1 Discussion— As an example, the site assessment
3.2.42.1 Discussion—These may include chemical collects data on soil, ground water and surface water quality,
E2081 − 22
land and resource use, potential receptors, and potential rel- 3.2.60.1 Discussion— The decisions involve regulatory
evantecologicalreceptorsandhabitats,andgeneratesinforma- policies, value judgments, different stakeholder decisions and
tion to develop a site conceptual model and to support using professional judgment to evaluate available information,
risk-based decision-making. The user is referred to Guides therefore, there may be more than one scientifically support-
D6235 and E1903 and other references in Appendix X9 for able answer for any particular technical policy decision. The
more information. choicesrepresentdifferentapproaches.Theusershouldconsult
the regulatory agency requirements to identify the appropriate
3.2.52 site conceptual model—Theintegratedrepresentation
technical policy decisions prior to implementing the RBCA
of the physical and environmental context, the complete and
process. Examples of technical policy decisions are, data
potentially complete exposure pathways and the potential fate
quality objectives, target risk levels, land use, ground water
and transport of chemical(s) of concern at a site.
use, natural resource protection, relevant ecological receptors
3.2.52.1 Discussion—The site conceptual model (some-
and habitats, stakeholder notification and involvement and
times called conceptual site model) should include both the
exposure factors.
current understanding of the site and the understanding of the
potential future conditions and uses for the site. It provides a
3.2.61 Tier 1 Evaluation—A risk-based analysis utilizing
methodtoconducttheexposurepathwayevaluation,inventory
non-site-specific corrective action goals for complete and
the exposure pathways evaluated, and determine the status of
potentially complete direct and indirect human exposure path-
the exposure pathways as incomplete, potentially complete or
ways and qualitative ecological screening evaluation for com-
complete.The userisreferredtoGuidesE1689,E2531,E3248,
plete and potentially complete exposure pathways for relevant
and ISO 21365:2019
ecological receptors and habitats.
3.2.53 site conditions—A general description of a site’s 3.2.61.1 Discussion—The non-site-specific corrective ac-
chemical, physical or biological characteristics that relate to tion goals developed for human exposure pathways are based
potential exposures to receptors or relevant ecological recep- on conservative assumptions (for example, exposure factors,
tors and habitats. fate and transport parameters) and methodologies (for
example, algorithms, analytical models) to estimate the non-
3.2.54 site-specific—Activities,informationanddataunique
site-specific values. The Tier 1 exposure pathways for human
to a particular site.
receptorsassumethatthereceptorandthesourcearelocatedin
3.2.55 site-specific ecological criteria (SSEC)—Risk-based
the same location. A qualitative ecological screening evalua-
qualitative or quantitative criteria for relevant ecological re-
tionisconductedthatmaybecombinedwithRESCtoevaluate
ceptors and habitats identified for a particular site under the
the potential exposures to relevant ecological receptors and
Tier 2 or Tier 3 evaluations.
habitats.TheTier1evaluationforsomechemical(s)ofconcern
3.2.55.1 Discussion—These may include chemical
orexposurepathwaysmayalsobebasedoncomparisonofsite
concentrations, biological measures or other relevant generic
conditions to ORMC. The non-site-specific corrective action
criteria consistent with the technical policy decisions. SSEC
goals for complete and potentially complete exposure path-
may be revised as data are obtained that better describe the
ways are compared to site conditions to determine if further
conditions and the relevant ecological receptors and habitats.
corrective action is warranted.
3.2.56 site-specific target levels (SSTL)—Risk-based values
3.2.62 Tier 2 Evaluation—A risk-based analysis that in-
for chemical(s) of concern that are protective of human health
volves an incremental refinement of theTier 1 methodology to
for specified exposure pathways developed for a particular site
develop site-specific corrective action goals.
under the Tier 2 or Tier 3 evaluations.
3.2.62.1 Discussion—The Tier 2 evaluation for human ex-
3.2.57 source area(s)—The source area(s) is defined as the
posurepathwaysmayincludedevelopingstatisticallyrepresen-
location of non-aqueous phase liquid (NAPL) chemical, the
tativeconcentrationsofchemical(s)ofconcernforcomparison
locations of highest soil or ground water concentrations of the
to theTier 1 corrective action goals, back-calculating SSTLby
chemical(s)ofconcernorthelocationreleasingthechemical(s)
applying the direct exposure pathway corrective action goals
of concern.
establishedunderaTier1evaluationatsite-specificdetermined
3.2.58 stakeholders—Individuals,organizationsorotheren-
point(s) of exposure, developing SSTL for potential indirect
tities that directly affect or are directly affected by the correc-
exposure pathways at point(s) of exposure using site-specific
tive action.
conditionsandtheTier1methodology,ordevelopingSSTLfor
3.2.58.1 Discussion—Stakeholders include, but are not lim-
complete or potentially complete exposure pathways using
ited to, owners, buyers, developers, lenders, insurers, govern-
site-specific conditions for which no RBSLwere developed in
ment agencies and community members and groups.
Tier 1, or the evaluation may employ a combination of
3.2.59 standard—As used in ASTM, a document that has
alternatives. For relevant ecological receptors and habitats, the
beendevelopedandestablishedwithintheconsensusprinciples
Tier 2 evaluation may involve additional qualitative or quan-
of the Society and that meets the approval requirements of
titativeanalyses.TheTier2evaluationforsomechemical(s)of
ASTM procedures and regulations.
concern and exposure pathways may also be based on com-
3.2.60 technical policy decisions—The choices specific to parison of site conditions to ORMC. The corrective action
the user that are necessary to implement the Risk-Based goals for complete and potentially complete exposure path-
Corrective Action framework described in this guide at a ways are compared to site conditions to determine if further
particular site. corrective action is warranted.
E2081 − 22
3.2.63 Tier 3 Evaluation—A risk-based analysis that in- 4.2 Risk assessment is a developing science. The scientific
volves a significant incremental effort over the Tier 2 evalua- approach used to develop the RBSL and SSTL may vary by
tion to develop site-specific corrective action goals. regulatory agency and by user due to regulatory requirements,
guidance and use of alternative scientifically-based methods.
3.2.63.1 Discussion—The Tier 3 evaluation for human ex-
posurepathwaystypicallyusesadvancedexposureassessment,
4.3 Activities described in this guide should be conducted
toxicity and risk assessment techniques (for example, probabi-
by persons familiar with current site characterization
listic exposure assessment methods, use of bio-availability
techniques, remedial action science and technology, current
data, use of advanced fate and transport modeling) allowing
human health risk and exposure assessment methodologies,
maximum flexibility to develop SSTL for potential direct and
toxicology, and current ecological evaluation methodologies.
indirectexposurepathwaysatthepoint(s)ofexposurebasedon
4.4 In order to properly apply the RBCA process, the user
site-specific conditions. A Tier 3 evaluation for relevant eco-
should AVOID the following:
logical receptors and habitats is typically more quantitative in
4.4.1 Prescribing Tier 1 RBSL or RESC as remedial action
nature and uses more site-specific data than previous tiers.The
standards for all sites rather than screening levels,
Tier 3 evaluation for some chemical(s) of concern and expo-
4.4.2 LimitinguseoftheRBCAprocesstoTier1evaluation
sure pathways may also be based on comparison of site
only and not continuing withTier 2 orTier 3 analyses for sites
conditions to ORMC.The corrective action goals for complete
where further tier evaluation is appropriate,
and potentially complete exposure pathways are compared to
4.4.3 Placing arbitrary time constraints on the corrective
site conditions to determine if further corrective action is
action process; for example, requiring that Tiers 1, 2, and 3 be
warranted.
completed within time periods that do not reflect the actual
3.2.64 user—An individual or group involved in the RBCA
urgency of and risks posed by the site,
process including owners, operators, regulators, UST fund
4.4.4 Using the RBCA process only when active remedial
managers, federal government case managers, attorneys,
action is not technically feasible, rather than as a process that
consultants, legislators and other stakeholders.
is applicable during all phases of corrective action,
3.2.64.1 Discussion—Two specific cases of users are envi-
4.4.5 Conducting active remedial action to achieve only
sioned. The first is the individual or group addressing a site or
technology-based remedial limits (for example, asymptotic
sitesunderthecircumstanceswherethereisnospecificagency
levels) prior to determining applicable corrective action goals,
program or there are multiple agency programs applicable to
4.4.6 Using predictive modeling that is not supported by
their project. The second is a regulatory agency that is
available data or knowledge of site conditions,
developing a comprehensive corrective action program.
4.4.7 Limiting remedial action options to a single class of
3.3 Acronynms and Abbreviations:
remedial actions for all sites (for example Guide E1943),
3.3.1 COC—chemicals of concern
4.4.8 Using unjustified or inappropriate exposure factors,
4.4.9 Usingunjustifiedorinappropriatetoxicityparameters,
3.3.2 ITRC—Interstate Technology and Regulatory Council
4.4.10 Failing to consider cumulative risks and additive
3.3.3 ORMC—other relevant measurable criteria
effects when evaluating multiple chemicals,
3.3.4 PFAS—Per- and polyfluoroalkyl substances
4.4.11 Excluding the evaluation of options for activity and
...