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ASTM User Training

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Title: RBCA for Chemical Releases Subject: RBCA Training Presentation Author: Jim Rocco Keywords: Risk, ASTM, RBCA, Chemicals Description: Introduction to RBCA – PowerPoint PPT presentation

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Title: ASTM User Training


1
ASTM User Training
  • in
  • Risk-Based Corrective Action for Chemical
    Releases
  • (Provisional ASTM Standard Guide)
  • Day 1

2
Course Objectives
  • Provide an understanding of the risk-based
    decision process.
  • Discuss the importance of Technical Policy
    Decisions
  • Emphasize the importance of the development and
    application of the site conceptual model

3
Course Objectives
  • Provide an understanding of the development of
    corrective action performance goals and the role
    of risk assessment and fate and transport in the
    risk-based decision process
  • Discuss the issues and processes necessary to
    make Tier decisions
  • Discuss the evaluation and selection of remedial
    action options

4
Course Expectations
  • Elementary understanding of the basic science
    necessary to make risk-based decisions
  • Understanding of the concepts and process
    necessary to implement a framework for making
    risk-based decisions
  • Understanding of the applicability of the RBCA
    framework to a variety of sites
  • Understanding of the issues related to the
    integration of the RBCA framework into an
    existing regulatory program

5
Course Expectations
  • This course is NOT intended to provide specific
    applications to existing regulatory programs
  • This course is NOT intended to provide all the
    tools necessary to perform risk-based decisions

6
Agenda Day 1
  • 800 - 830 Introduction
  • 830 - 930 Summarizing the Framework
  • 930 - 945 Break
  • 945 - 1045 Summarizing the Framework
  • 1045 - 1100 Break
  • 1100 -1200 Technical Policy Decisions
  • 1200 - 100 Lunch
  • 100 - 215 Technical Policy Decisions
  • 215 - 230 Break
  • 230 - 400 Developing the Site Conceptual
    Model
  • 400 - 415 Break
  • 415 - 500 Developing the Site Conceptual Model

7
Agenda - Day 2
  • 800 - 930 RBSL/SSTL Development
  • 930 - 945 Break
  • 945 - 1045 RBSL/ SSTL Development
  • 1045 - 1100 Break
  • 1100 -1200 RESC/SSEC Development/Data
    Collection
  • 1200 - 100 Lunch
  • 100 - 230 Tier Decisions/Remedial Options
  • 230 - 245 Break
  • 245 - 400 Source Reduction/ Activity and Land
    Use Controls
  • 400 - 415 Break
  • 415 - 500 Factors for Consideration in
    Remedial Action Selection

8
Who is ASTM?
ASTM is an organization that has historically
focused on promulgating standards for engineering
tests and specifications for engineering
materials.
ASTM standards are developed through a rigorous
consensus-building process, that may also include
external peer review (as in the case of RBCA).
Members vote to approve standards, and all
negative ballots must be resolved.
9
ASTM RBCA
Authored by a multi-functional and
multi-disciplinary group of ASTM E-50
Subcommittee members, representing
  • State Regulators
  • USEPA Staff
  • Insurance Industry
  • Banking Industry
  • Chemical Industry
  • Oil Industry
  • Academia
  • Consulting
  • Reimbursement Fund Managers
  • Regulatory Managers
  • Hydrogeologists
  • Toxicologists
  • Environmental Engineers
  • Environmental Scientists
  • Modelers

10
Risk-Based Corrective Action (RBCA) Process
RBCA is a framework developed by ASTM in which
exposure and risk assessment practices are
integrated with traditional components of the
corrective action process.
  • RBCA Goals
  • protection of human health and environment
  • consistent and technically-defensible decisions
  • selection of appropriate and resource-efficient
    remedies
  • optimal allocation of limited resources
  • practical and resource-efficient approach
  • achievement of corrective action and
    redevelopment together

11
Why 3 Tiers (Levels) in RBCA?
Tier 3
Less Site-Specific Uncertainty
Greater Site-Specific Effort
Tier 2
Tier 1
Target Risk
Every tier achieves the same level of public
health protection
12
How is a RBCA Program Developed?
  • ASTM Risk-Based Corrective Action for Chemical
    Release Sites
  • outlines a framework for integrating exposure and
    risk assessment practices with traditional
    components of the corrective action process.
  • describes steps and philosophy to build the
    framework and to incorporate technical policy
    decisions into corrective action programs.
  • identifies stakeholders and stakeholder
    involvement in the program development

Technical Policy Decisions
Regulatory Program
RBCA Framework
13
How is a RBCA Program Implemented?
  • ASTM Risk-Based Corrective Action for Chemical
    Release Sites
  • provides mechanism for stakeholder involvement
  • makes technical policy decisions
  • integrates framework into regulatory program
  • provides training for stakeholders

Technical Policy Decisions
Regulatory Program
RBCA Framework
14
RBCA Customization Technical Policy Decisions
Policy
  • Target risk limits
  • Land use issues
  • Ground water use issues
  • Chemical(s) of concern
  • Data requirements
  • Site classification procedures
  • Exposure assumptions and pathways
  • Point(s) of demonstration
  • Fate and transport
  • natural attenuation
  • modeling procedures
  • Remedy selection criteria
  • Interim remedial action
  • Institutional controls
  • Engineering controls
  • mass reduction vs. risk reduction
  • Stakeholder involvement

15
Summarizing the Framework
16
Definitions
17
Definitions
  • The Corrective Action Process
  • the sequence of actions that include site
    assessment and investigation, interim remedial
    action, remedial action, operation and
    maintenance of equipment, monitoring of progress,
    and termination of the remedial action.
  • Chemical Release
  • any spill or leak or detection of concentrations
    of chemical(s) of concern in environmental media

18
Definitions
  • Risk Assessment
  • an analysis of the potential for adverse effects
    on receptors and relevant ecological receptors
    and habitats caused by a chemical(s) of concern
    from a site
  • the basis for the development of corrective
    action goals and determination of the need for
    interim remedial action, remedial action or a
    combination of these actions

Risk Toxicity Exposure
Exposure Concentration Intake
19
Definitions
  • Technical Policy Decisions
  • the choices specific to the user that are
    necessary to implement the Risk-Based Corrective
    Action framework
  • involve professional judgment to evaluate
    available data
  • may be more then one scientifically supportable
    answer
  • the choices represent different approaches
  • appropriate technical policy decisions may have
    already been made by the regulatory agency
  • Examples of technical policy decisions
  • data quality objectives, target risk levels, land
    use, ground water use, natural resource
    protection, relevant ecological receptors and
    habitats and exposure

20
Definitions
  • Chemical(s) of Concern (CoCs)
  • specific constituents and their breakdown
    products that are identified for evaluation
  • identification can be based on their historical
    and current use at a site, detected
    concentrations in environmental media and their
    mobility, toxicity, and persistence in the
    environment

21
ASTM Risk-Based Corrective Action (RBCA)
Flowchart
Decision Point?
Decision Point?
Decision Point?
Decision Point?
Decision Point?
Decision Point?
Decision Point?
Decision Point?
Decision Point?
Decision Point?
22
Initial Site Assessment
  • Identify all available information concerning
  • nature of the release
  • physical condition and setting of the site
  • environmental condition of the site
  • Focus on developing the site conceptual model
  • identifying incomplete exposure pathways
  • Determine if further action is necessary

23
Initial Site Assessment
  • Non-intrusive and intrusive data collection
    activity to support
  • initial response action evaluation
  • risk reduction activities
  • refinement of site conceptual model
  • comparison of concentrations of chemical(s) of
    concern in environmental media to risk-based
    screening levels (RBSL)
  • comparison of site conditions to relevant
    ecological screening criteria (RESC)

24
Initial Response Action Risk Reduction
Risk Reduction Activity
Risk
Initial Response Action
25
Initial Site Assessment Source(s) and Source
Area(s)
Source Area(s) - the location of non-aqueous
phase liquid (NAPL) chemical, the locations of
highest soil or ground water concentrations of
the chemical(s) of concern or the location
releasing the chemical(s) of concern
26
Initial Site Assessment Transport Mechanisms
Atmospheric fate transport
deposition
Dust to air
Site
Off-Site
Runoff
Soil to air
Soil to Ground Water
Ground Water to Air
Ground Water Transport
Chemical(s) of concern dissolved in ground water
27
Initial Site Assessment Receptors
Industrial land use
Future land use ?
Residential land use
Off-Site
Site
Receptors
28
Initial Site Assessment Relevant Ecological
Receptors and Habitats
  • Ecological resources that are to be protected are
  • communities with threatened and endangered
    species
  • recreationally or commercially important
    communities
  • that are regionally or nationally rare
  • communities with high aesthetic quality
  • communities that afforded special protection by
    law or regulation
  • habitats that support these communities.
  • Identification may come from applicable federal
    and state regulations

29
Initial Site Assessment Point(s) of Exposure
Site
Off-Site
Point(s) of Exposure
Point(s) of Exposure - The point(s) at which an
individual or population may come in contact with
a chemical(s) of concern originating from a site.
30
Tier 1 Evaluation Exposure Pathway
Exposure Pathway - describes a mechanism by which
an individual or population is exposed to a
chemical(s) of concern and includes a source or
source area, a transport/exposure medium (e.g.,
air or water), a point of exposure, and an
exposure route.
31
Site Conceptual Model
Site Conceptual Model - The integrated
representation of the physical and environmental
context, the complete and potentially complete
exposure pathways and the likely distribution of
chemical(s) of concern at a site
32
Risk-Based Screening Levels (RBSL)
  • Represent concentrations that satisfy the
    criteria for Not Further Action at Tier 1
  • RBSL typically quantitative
  • Use conservative values for risk and exposure
    assumptions
  • May use regulatory values
  • MCL, aesthetic values (taste or odor)

33
Ecological issues within the RBCA process
  • RBCA framework can be used to evaluate ecological
    risk
  • Ecological risk can follow a tiered process
  • PS-104 provides guidance on how to get started
  • Specific guidance is under development
  • Responses tend to be evaluated for
    populations/ecosystems, rather than individuals
  • Guidelines for Ecological Risk Assessment
    EPA/630/R-95/002F, 4/98, Final

34
Relevant Ecological Screening Criteria (RESC)
  • Non-site-specific
  • Used in the Initial Site Assessment and Tier 1
    evacuation
  • Part of the technical policy decisions
  • Can be qualitative or quantitative in nature
  • qualitative - waterfowl feeding and nesting
  • quantitative - water quality criteria
  • Can be based on concentrations of chemical(s) of
    concern or biological measures

35
Tier 1 Evaluation Risk-Based Screening Levels
CRBSL
Site
Off-Site
CRBSL
Point(s) of exposure is assumed to be located
proximal to the source area(s)
CRBSL
CRBSL
CRBSL
CRBSL
CRBSL
  • Compare highest concentrations of chemical(s) of
    concern to RBSL for complete and potentially
    complete exposure pathways
  • Compare site conditions to RESC

36
Tier 1 Decisions Factors
  • The basis for the RBSL or RESC are not
    representative of the site-specific conditions
  • hydrogeology, exposure parameters, point(s) of
    exposure, reasonable land use options
  • The RBSL or RESC do not exist for a complete and
    potentially complete exposure pathway
  • An unacceptable risk to a relevant ecological
    receptor or habitat is identified during the Tier
    1 qualitative ecological screening evaluation

37
Tier 1 Decisions Factors
  • Site-specific target levels (SSTL) or
    site-specific ecological criteria (SSEC)
    developed under further tier evaluation will be
    significantly different than the RBSL or RESC or
    will significantly modify the remedial action
    activities
  • The cost of remedial action based on RBSL will
    likely be greater than further tier evaluation
    and subsequent remedial action.

38
Tier 1 Outcomes
  • No further action
  • if the concentrations of the chemical(s) of
    concern are below the RBSL
  • if the comparison of the site conditions to RESC
    indicate that there is no unacceptable risk to
    relevant ecological receptors and habitats
  • Compliance monitoring
  • not confident that data support the conclusion
    that concentrations will not be above RBSL in the
    future
  • to collect data sufficient to confidently
    conclude that concentrations will not be above
    RBSL in the future.

39
Tier 1 Outcomes
  • Interim remedial action
  • address most significant concerns in an expedited
    fashion
  • Remedial action
  • reduce concentrations of chemical(s) of concern
    at the point(s) of exposure
  • eliminate a complete or potentially exposure
    pathway
  • address an unacceptable risk

40
Tier 1 Outcomes
  • Further Tier evaluation
  • complete and potentially complete exposure
    pathways with concentrations of chemical(s) of
    concern above RBSL or do not meet RESC
  • maintains the same level of protectiveness, but
    uses site specific data to help make better
    informed decisions.

41
Tier 2 SSTL
  • Develop SSTL using RBSL methods, but replace
    default assumptions with site-specific parameters
  • compare to concentrations of chemical(s) of
    concern in the source area(s)
  • Develop statistical representation of source area
    concentrations of chemical(s) of concern when
    appropriate data exist
  • compare to RBSL or SSTL developed by using
    site-specific parameters

42
Tier 2 SSTL and SSEC
  • Develop SSTL by applying RBSL at point(s) of
    exposure and back-calculating SSTL for
    chemical(s) of concern at source area(s)
  • evaluate fate and transport of chemical(s) of
    concern in environmental media
  • based on estimated, measured, or monitored
    attenuation
  • Develop SSEC for relevant ecological receptors
    and habitats based on additional qualitative or
    quantitative analyses

43
Example Tier 2 Evaluation
  • Substituting site-specific parameters in RBSL
    method

W source width parallel to ground water flow
m dGW thickness of ground water mixing zone
m I infiltration rate m/y V ground water
flow velocity m/y CW dissolved concentration
in vadose zone source area mg/l CGW dissolved
concentration in ground water source area mg/l
44
Example Tier 2 Evaluation
  • Statistical representation of source area
    concentrations

45
Example Tier 2 Evaluation
  • Back-calculating SSTL at source area(s) by
    applying RBSL at point of exposure

Site
Off-Site
Site-Specific Target Level Applied at Source Area
Source Area
Csoil
RBSL Applied at Point of Exposure
Cgw
Cpoe
46
Example Tier 2 Evaluation
  • Back-calculating SSTL at source area(s) by
    applying RBSL at point of exposure

Cgw(x) CW f (degradation, seepage velocity,
thickness of source zone, dispersion) Cgw
chemical of concern along centerline of the
plume CW steady state source concentration
47
Example Tier 2 Evaluation
  • Tier 2 site-specific ecological criteria (SSEC)
  • used in Tier 2 evaluations
  • usually quantitative in nature
  • part of technical policy decisions
  • Tier 2 refines Tier 1 RESC with more
    site-specific parameters
  • refine a model by using site-specific soil
    characteristics
  • use a toxicity value that is more appropriate for
    a relevant ecological receptor or habitat at the
    site

48
Tier 2 - Point(s) of Demonstration
Site
Off-Site
Source Area
Csoil
Cgw
Cpod
Cpoe
Point(s) of Demonstration - A location(s)
selected between the source area(s) and the
potential point(s) of exposure where
concentrations of chemical(s) of concern must be
at or below the determined target levels in media
(e.g., ground water, soil or air).
49
Tier 2 Decisions Factors
  • The basis for the SSTL or SSEC are not
    representative of the site-specific conditions
  • hydrogeology, exposure parameters, point(s) of
    exposure, reasonable land use options
  • The SSTL or SSEC do not exist for a complete and
    potentially complete exposure pathway
  • An unacceptable risk to a relevant ecological
    receptor or habitat is identified during the Tier
    2 comparison to SSEC

50
Tier 2 Decisions Factors
  • Site-specific target levels SSTL or SSEC
    developed under further tier evaluation will be
    significantly different than the SSTL or SSEC or
    will significantly modify the remedial action
    activities
  • The cost of remedial action based on SSTL will
    likely be greater than further tier evaluation
    and subsequent remedial action.

51
Tier 2 Outcomes
  • No further action
  • if the concentrations of the chemical(s) of
    concern are below the SSTL
  • if the comparison of the site conditions to SSEC
    indicate that there is no unacceptable risk to
    relevant ecological receptors and habitats
  • Interim remedial action
  • address most significant concerns in an expedited
    fashion

52
Tier 2 Outcomes
  • Remedial action
  • reduce concentrations of chemical(s) of concern
    at the point(s) of exposure
  • eliminate a complete or potentially exposure
    pathway
  • address an unacceptable risk
  • Further Tier evaluation
  • complete and potentially complete exposure
    pathways with concentrations of chemical(s) of
    concern above SSTL or do not meet SSEC
  • maintains the same level of protectiveness, but
    uses site specific data to help make better
    informed decisions.

53
Tier 3 SSTL and SSEC
  • Tier 3 involves the highest level of
    sophistication and resources
  • the development and use of site-specific
    numerical models
  • use of probabilistic data representations
  • address variability and uncertainty
  • development of site-specific exposure factors,
    exposure scenarios, toxicity data,
    bioavailability, and biomagnification
  • Requires significantly more detailed
    site-specific data collection

54
Example Tier 3 Evaluation
  • Uncertainty and Probabilistic Analysis
  • Uncertainty represents ignorance or lack of
    perfect knowledge about poorly characterized
    phenomena or models
  • addressed in Tier 1 by conservative assumptions
  • addressed in Tier 2 by site-specific measurements
  • addressed in Tier 3 by better measurements or
    probabilistic analysis
  • Probabalistic analysis is the use of
    distributions of input values

55
Example Tier 3 Evaluation
  • Bioavailability, biodegradation and
    biomagnification
  • bioavailability is a measure of the fraction of
    the chemical(s) of concern in environmental media
    that is accessible to an organism for absorption
  • biodegradation is natural plant, animal or
    microbial metabolism that results in the
    reduction of mass of chemical(s) of concern
  • biomagnification a measure of the fraction of
    chemical(s) of concern that transfer and
    accumulate in a organism as a result of food web
    consumption

56
Example Tier 3 Evaluation
  • Tier 3 site-specific ecological criteria
  • used in Tier 3 evaluations
  • usually quantitative in nature
  • part of technical policy decisions
  • Tier 3 completely site-specific and refines Tier
    2 SSEC
  • use a toxicity value that is more appropriate for
    a relevant ecological receptor
  • can involve lab toxicity studies applicable to
    ecological exposure
  • e.g., round worm exposure tests in soil

57
Tier 3 Outcomes
  • No further action
  • if the concentrations of the chemical(s) of
    concern are below the SSTL
  • if the comparison of the site conditions to SSEC
    indicate that there is no unacceptable risk to
    relevant ecological receptors and habitats
  • Interim remedial action
  • address most significant concerns in an expedited
    fashion

58
Tier 3 Outcomes
  • Remedial action
  • reduce concentrations of chemical(s) of concern
    at the point(s) of exposure
  • eliminate a complete or potentially exposure
    pathway
  • address an unacceptable risk

59
Remedial Action Option Evaluation
  • Effectiveness of the remedial action in
    protecting human health and the environment,
  • Long-term reliability and probable success in
    meeting the remedial action goals now and in the
    future,
  • Short-term risks posed by the implementation of
    the remedial action,
  • Amenability of the remedial action to integration
    with property redevelopment plans,

60
Remedial Action Option Evaluation
  • Acceptability of the remedial action to the
    stakeholders,
  • Implementability and technical practicability of
    the remedial action, and
  • The cost-effectiveness of the options to meet the
    remedial action goals.

61
Remedial Action Plan
  • Based on the appropriate RBSL, SSTL, RESC, SSEC
    or remedial action goals , source area(s) and
    point(s) of exposure, choose measures to achieve
    the corrective action goals or eliminate exposure
    pathways
  • Remedial options may include combinations of
    active and passive measures

Weight of considerations are based on a technical
policy decision
  • Considerations
  • source removal or reduction
  • eliminate exposure
  • natural attenuation
  • engineering controls
  • institutional controls

62
Monitoring Program
  • Following, or during remedial action, a
    monitoring plan is needed to insure that the
    appropriate RBSL, SSTL, RESC, SSEC or remedial
    action goals established in the Tier analysis
    continue to be met
  • Verify assumptions and predictions used in Tier 2
    and Tier 3.

63
No Further Action and Conditions of Closure
  • Ease of obtaining an NFA is related to confidence
    in supporting data and requirements of the
    governing regulatory framework
  • Example NFA letter contents
  • reservation of rights / re-opener clauses
  • monitoring requirements
  • demonstrate the effectiveness of implemented
    remedial action
  • confirm that current conditions persist or will
    improve with time
  • maintenance requirements
  • ensure integrity and continued performance
  • financial responsibility provisions

64
Technical Policy Decisions
  • RBCA How to Implement a Program

65
Technical Policy Decisions
  • Assumptions and values used in the risk-based
    decision process to ensure that decisions are
    protective of human health and the environment
  • set the floor
  • made up front
  • performance-based
  • acceptable levels of conservatism and uncertainty
  • involve professional judgment
  • more than one scientifically supportable answer
    possible
  • include social, economic and other considerations

66
Technical Policy Decisions
Scientific
Regulatory Driven Decisions made as part of a
regulatory program that apply to all sites or a
set of circumstances
Site Driven Decisions made at an individual site
based on site-specific circumstances
Technical and Policy Decisions
Political and Social
Economic
Business Driven Decisions made at an individual
site based on business-specific circumstances
67
Topics
  • Identify some of the more controversial topics
  • stakeholder involvement
  • ground water resource and use
  • point(s) of demonstration
  • uncertainty and conservatism
  • data quantity and quality objectives
  • adequacy of site assessment
  • target risk and hazard quotient
  • activity and land use
  • ecological risk

68
Stakeholder Involvement
  • Who are they?
  • When do they get involved?
  • How should they be involved?
  • regulatory program development
  • site-specific decisions
  • informational

69
Stakeholder Involvement Who are They?
  • Regulatory agency
  • Owners
  • Community
  • Real estate interests
  • Financing interests
  • State and local government
  • Environmental groups

70
Stakeholder Involvement Program Element
  • Many state and federal programs develop
    regulations, policies and guidelines with
    specific consensus building requirements and
    formal or informal requirements for
    representation by balanced stakeholder groups.
  • It is extremely important for the program
    development process to consider the use of such
    representation to reach consensus on some of the
    widely debated issues which could impact the
    application and implementation of the RBCA
    process.

71
Stakeholder Involvement Site-Specific Element
  • The level of site-specific involvement will
    depend on the type and severity of the situation
  • land and activity use decisions
  • impact to surrounding areas
  • community concerns

72
Stakeholder Involvement Informational
  • Constructive dialog that acknowledges the needs
    and expectations of the stakeholders
  • Education and outreach
  • Identify stakeholder concerns on potential
    corrective action

73
Class Exercise ?? Site-Specific Stakeholder
Involvement
  • A truck spills 20 gallons of diesel fuel on the
    interstate highway
  • who to tell?
  • who to ask?

74
Class Exercise ?? Site-Specific Stakeholder
Involvement
  • How about this stuff?
  • bottles of discarded ant poison, circa 1930s
  • suburban residential neighborhood.

75
Corrective Action Goals
  • What are the appropriate goals for corrective
    action?
  • background
  • analytical detection limits
  • generic standards
  • technical impracticability
  • financial impracticability
  • site-specific risk-based
  • environmentally acceptable endpoints

76
Chemical(s) of Concern
  • What is the criteria for selection of chemical(s)
    of concern and indicator chemicals?
  • all chemicals based on analytical detection
  • specific chemicals based on knowledge of material
    released

77
Decision Criteria
  • What criteria should be considered when making
    decisions?
  • timing
  • long and short term reliability
  • implementability
  • costs
  • acceptability to stakeholders
  • others?

78
Fate and Transport
  • What criteria should be used to select models to
    predict fate and transport of a chemical?
  • model performance-based
  • strict list of acceptable models

79
Exposure Pathways
  • What is the process for identifying exposure
    pathways and receptors for consideration and the
    criteria for exclusion or elimination of an
    exposure pathway?
  • documentation and tracking requirements
  • hierarchy of land use and resource use criteria

80
Technical Policy Decision Ground Water Resources
and Use
  • What criteria should be used to determine the
    need and extent for restoration of ground water
    and beneficial resources?
  • drinking water everywhere and always
  • current and potential future use determination
  • classification of ground water
  • yield rates
  • quality (e.g. presence of salt water or nitrates)
  • hydrogeologic considerations - barriers and
    confining layers
  • ecosystem impacts, surface water connection
  • natural resource value

81
Technical Policy Decision Ground Water Resources
and Use
  • What criteria should be used to determine the
    need and extent for restoration of ground water
    and beneficial resources?
  • Classification of ground water is a technical
    policy decision
  • Classification decisions may consider
  • yield rates
  • quality (e.g. presence of salt water or nitrates)
  • hydrogeologic considerations - barriers and
    confining layers

82
Future Use of Groundwater
  • Drinking water everywhere and always
  • Other extreme never any water use anywhere.
  • Consensus on this issue is important to implement
    RBCA

83
Consensus
  • What is the most effective compromise on
    groundwater issues which best balances social,
    scientific and financial concerns?
  • Examples time (natural attenuation) or location
    (off-site plume) exceptions to DW.

84
Class Exercise ??
  • Rural area on growing suburban fringe and no
    municipal drinking water supply

85
Class Exercise ??
  • RCRA facility with municipal drinking water
    supply and river greater then 3 miles from the
    facility

86
Summary of Ground Water Resources and Use Issues
  • How did you come to a decision in your group?
  • What did you decide and why?
  • Did you consider drinking water as well as
    agricultural uses?
  • Did you provide for exceptions to your
    classification scheme?

87
Point of Demonstration for Chemicals in the
Ground Water
  • Where should the point(s) of demonstration be
    located?
  • at the property line?
  • at points defined by regulation
  • at site-specific determined point(s) of exposure?
  • different application for current potential
    exposures and future potential exposures
  • at the point of access for water uses?

88
Point of Demonstration for Chemicals in the
Ground Water
  • How should travel time be accounted for?
  • What are the contingency ways to prevent contact
    with a receptor?
  • What soil and bedrock characteristics will
    contribute to natural attenuation?

89
Uncertainty
  • How should uncertainty be addressed?
  • better measurements
  • conservative assumptions
  • probabilistic analyses
  • This issue exists in many endeavors.
  • Learn how to manage uncertainty early on in the
    RBCA Process

90
Managing Uncertainty
  • How will Data be Used?
  • physical, chemical and hydrogeolocical data
  • What quantity and quality of data is required?
  • indicators and screening
  • confirmatory and detailed site-specific
  • practical quantitation limits.
  • minimum number of samples
  • the safety net
  • the statistical approach.

91
Managing Uncertainty
  • Better measurements needed to address both
  • variability (true heterogenuity in a
    well-characterized phenomenon, cannot be reduced
    by further measurements) and
  • uncertainty (ignorance about a poorly
    characterized phenomenon that can be reduced
    through further measurements).

92
Managing Uncertainty
  • Uncertainty can be addressed by better
    measurements or by making conservative
    assumptions.
  • The effect of conservative assumptions is to
  • overestimate mass
  • overestimate concentrations at the point(s) of
    exposure
  • overestimate resulting doses
  • overestimate health effects

93
Managing Uncertainty
  • Conservatism assumptions may result in an
    overestimate of
  • mass of chemical(s) of concern
  • concentrations at the point(s) of exposure
  • doses to receptors
  • health effects on receptors

94
Cancer and Non-Cancer Risk
  • What is the appropriate target risk and how
    should cumulative and additive effects be
    treated?
  • used to calculate screening levels and
    site-specific levels
  • cancer
  • individual chemical
  • cumulative of all carcinogenic chemicals
  • non-cancer
  • individual chemical
  • additive of all non-carcinogenic chemicals

95
Cancer Risk Target Risk Levels
  • USEPA excess lifetime cancer risk range
  • EPAs guidance (OSWER Directive 9355.0-30)
  • Where cumulative carcinogenic site risk to an
    individual based on reasonable maximum exposure
    for both current and future land use is less than
    10-4 , action is generally not warranted.
  • Action may be taken at less than 10-4 based on
    site-specific concerns, but all records of
    decisions for remedial actions taken at sites
    posing risks within 10-4 to 10-6 must explain why
    remedial action is warranted.

96
Cancer Risk Excess vs. Total Cancer Risk
Background Risk Existing risk of cancer
incidence. Excess Risk Additional risk of
cancer incidence due to exposure to site
constituents.
97
Cumulative Cancer Risks Example
  • Massachusetts has a significant risk definition
    of 1 X 10-5 for total site cancer risk.
  • Method 1 Tables and Method 2 formulas are based
    on a 1X10-6 for individual chemicals where there
    are no more than 10 chemicals.
  • Method 3 total site risk may not exceed 1 X 10-5
  • Texas Risk Reduction Program
  • has a significant risk definition of 1 X 10-5 for
    individual chemicals
  • requires a cumulative adjustment to 1 X 10-5
    where there are more then 10 chemicals

98
Non-Cancer Hazard Quotient
  • Quantifying non-cancer effects
  • evaluated by comparing the estimated dose with a
    reference dose
  • ratio is called the Hazard Quotient
  • a Hazard Quotient of less than one is typically
    considered to be of no concern.

99
Additive Non- Cancer Risks Example
Risk for a single chemical in Tier 1
Risk of all chemicals in Tier 3
100
Adequacy of Site Assessment
  • How much site assessment is necessary?
  • Command and Control approach the full vertical
    horizontal extent of contamination.
  • The prescriptive approach three groundwater
    wells, 10 foot grids and thousands of soil
    samples.
  • The compromise Data quality objectives and how
    the data will be used.
  • Safety net issues.

101
Data Quantity and Quality
  • What quantity and quality of data is appropriate
    to make corrective action decisions?
  • how will data be used?
  • indicators and screening
  • confirmatory and detailed site-specific
  • statistical representations
  • fate and transport modeling
  • what type of data is needed
  • physical, chemical and hydrogeological data

102
Activity and Land Use
  • How can land and activity uses other than
    residential land use be established for a
    property?
  • how to define residential, commercial, industrial
    or other activities
  • use of institutional controls
  • How effective are land and activity use controls
    in ensuring that future users will not be
    adversely affected if chemical(s) of concern
    remain at a site?
  • long term effectiveness and reliability of
    control
  • effects of current and future exposures to
    releases

103
Identification and selection of relevant
ecological receptors and habitats
  • General versus specific receptors
  • example
  • general - a surface water resource passing
    through a region
  • specific - a bald eagle in the wetlands adjacent
    to a site
  • could also include habitats
  • need to consider receptors/habitats and complete
    exposure pathways
  • what decision criteria will be used for the
    selection?

104
Identification and selection of relevant
ecological receptors and habitats
  • Societal versus scientific value
  • public perception does not always equate to
    ecological health
  • a recreational water body is devoid of fish and
    water fowl because the sediments supporting
    higher levels of aquatic life are non-existent
  • society looks at the recreational fish and
    aesthetics of the water fowl
  • scientists looks at the worms

105
Identification and selection of relevant
ecological receptors and habitats
  • Individual versus a population/community
  • individual considered only when rare, threatened
    or endangered species are involved
  • population/community is usually what is considered

106
Identification and selection of relevant
ecological receptors and habitats
  • Ecological risk assessment
  • utilize entry/exclusion criteria as relevant
    ecological screening criteria (RESC)
  • size of site or of population impacted
  • experience base and characteristics of the site
  • The process is parallel but much more complicated
    than for human health
  • Extensive problem formulation and regulatory
    discussions required
  • Re-evaluation is needed with new information

107
Wrap up
  • We have learned why the key technical policy
    decisions are important.
  • The decisions must be dynamic, not carved in
    stone and be flexible enough to
    change
    as the program changes.
  • Social and political considerations must be
    balanced with
  • The science of risk assessment and
  • Business and financial interests


108
Key Points
  • Three levels of decisions
  • the whole program, site-specific and
    business-specific.
  • consensus among stakeholders important at all
    levels.
  • decisions must deal with uncertainty
  • Important issues are
  • the level of stakeholder involvement
  • groundwater use and point of demonstration
  • target and cumulative or additive risk
  • adequacy of site assessment
  • land use
  • ecological risk assessment

109
Developing the Site Conceptual Model
110
Risk Management under RBCA
  • Planning and scoping
  • technical policy decisions
  • site conceptual model
  • Iterative evaluation
  • data collection
  • fate transport analyses
  • Risk-based decisions
  • further evaluation
  • remedial action
  • interim remedial action

111
Exposure Pathway
EXPOSURE ROUTES
TRANSPORT MECHANISMS
PRIMARY SOURCES
SECONDARY SOURCES
RECEPTORS


Affected Sub-surface Soils (gt 3 ft depth)
Above Ground Storage Tank Piping
GROUND WATER Potable Water Use
Commercial or Industrial Workers
Leaching and Ground Water Transport
  • Receptors
  • Residents
  • Commercial or Industrial workers
  • Construction workers
  • Recreational Users
  • Relevant Ecological Receptors and Habitats
  • Sources
  • Product Storage
  • Piping/Distribution
  • Operations
  • Waste Mgmt Units
  • Other
  • Source Area
  • Surface Soils
  • Subsurface Soils
  • Dissolved Ground Water Plume
  • Non-Aqueous Phase Liquid (NAPL)
  • Sediments
  • Transport Mechanisms
  • Wind Erosion Atmospheric Dispersion
  • Volatilization and Enclosed Space Accumulation
  • Leaching to Ground Water Transport
  • Mobile NAPL Migration
  • Storm water/Surface Water Transport
  • Exposure Routes
  • Dermal Contact
  • Ingestion
  • Inhalation of Particulate
  • Inhalation of Vapors
  • Potable Water Use
  • Ingestion
  • Cooking
  • Showering
  • Cleaning
  • Swimming

Source
Transport
Receptor
112
Site conceptual model (SCM)
  • An inventory of sources, transport mechanisms,
    and receptors
  • Exposure pathway analysis
  • focus on complete exposure pathways
  • current and reasonable potential future land and
    water use
  • hydrogeologic characteristics
  • Factor in characteristics of the material
  • both toxicity and physical/chemical
  • Account for potential mitigating factors
  • including regional characteristics

113
Site Conceptual Model Development
Initial Site Assessment
Initial SCM
  • Risk-based Decision
  • Remedial Action
  • Collect Additional data
  • Tier upgrade

Refined SCM
  • Working hypothesis of site management needs
  • Updated as new data become available
  • Valuable communication tool

114
Sources, Transport Mechanisms and Receptors
  • Source/Source Area
  • a source and mechanism for chemical release into
    the environment
  • physical/chemical, toxicological properties

115
Sources, Transport Mechanisms and Receptors
  • Means by which a chemical moves from source to
    receptor
  • transport medium (e.g., air, soil, ground
    water)
  • mechanism (e.g.,ground water flow, air dispersion)

116
Sources, Transport Mechanisms and Receptors
117
Sources, Transport Mechanisms and Receptors
  • Based on reasonable potential current future
    land and water use
  • residents - visitors
  • relevant ecological receptors habitats
  • reasonable potential future receptors

118
Sources, Transport Mechanisms and Receptors
  • Point of Exposure - A point of potential contact
    of the receptor with the medium
  • Route of Exposure - means for taking the chemical
    into the body

119
Sources, Transport Mechanisms and Receptors
  • Relevant ecological receptors and habitats
  • identify specifies and habitats
  • develop exposure scenarios
  • how do we identify?

120
Example of a conceptual model
121
Example of a conceptual model (ASTM PS-104-98)
122
Example of a conceptual model (RAGS Part D)
123
Another example of a conceptual model
From Guidelines for Ecological Risk Assessment,
EPA/630/R-95/002F, 4/98, Final
124
Exposure Pathway Analysis
  • For each complete exposure pathway, a
    quantitative evaluation of risk can be performed

125
Exposure Pathway Analysis
  • A quantitative evaluation of risk can be
    performed for each complete or potentially
    complete exposure pathway

126
Assessing risk along a pathway
Receptor
Transport
Source
Conceptual Model
127
Components of risk assessment
Health Risk
Toxicity
Dose
Exposure
Exposure Concentrations
Fate Transport
Source Concentrations
128
Risk Assessment Process
Source Concentrations
Exposure Concentrations
Health Risk
Dose
Exposure
Toxicity
Fate Transport
Transport Assessment
Source Characterization
Exposure Assessment
Risk Characterization
Dose- Response Assessment
129
Classic risk assessment paradigm
130
Ecological Risk Assessment
  • Follows a tiered evaluation similar to human
    health risk assessment
  • Parallel BUT NOT identical to human health risk
    assessment
  • Site conceptual model assists in
  • putting together scenarios
  • determining potential risk and exposure

131
Ecological Risk Assessment
  • Important questions in ecological risk assessment
    are
  • what is important to protect?
  • how do we identify relevant ecological receptors
    and habitats?
  • Requires extensive
  • problem formulation
  • discussion of technical policy decisions with the
    regulatory agencies

132
Risk Management under RBCA
  • Planning and scoping
  • technical policy decisions
  • site conceptual model
  • Iterative evaluation
  • data collection
  • fate transport analyses
  • Risk-based decisions
  • further evaluation
  • remedial action
  • interim remedial action

133
Exposure Assessment Data Collection
  • Primary objective
  • evaluate pathways in order to make risk-based
    decisions
  • Fundamentally need to address
  • what? where? how much? when?
  • uncertainty in estimate
  • Data quantity and quality needs vary with tiers
    and decision-points
  • screening level versus modeling effort versus
    validation

134
Exposure Assessment Sources
  • Chemicals of concern
  • e.g., physical, chemical, toxicological
  • Representative concentration
  • Physical setting
  • e.g., soil characteristics, hydrogeology, climate

135
Exposure Assessment Fate Transport
  • Partitioning between media
  • Cross-media transfers
  • soil-to-groundwater leaching
  • migration in groundwater
  • soil-to-air migration
  • Simple to more complex
  • Empirical versus modeling data
  • Variability and uncertainty

136
Exposure Assessment Other Considerations
  • Land and water use
  • reasonably current and potential
  • typically defines receptors
  • Pathway selection
  • fate transport important
  • Exposure assumptions
  • who, how much and how often
  • Chemical availability (bioavailability)
  • Variability and uncertainty

137
Toxicity assessment
  • Non-carcinogenic effects
  • leads to the development of malignant cells
  • reference Dose (RfD) (mg/kg-day) (oral, dermal)
  • reference Concentration (RfC) (mg/m3)
    (inhalation)
  • Carcinogenic effects
  • impacts the development, size or functioning of
    the whole body or specific organs (including skin
    and the nervous system) but does not lead to the
    development of malignant cells
  • cancer slope factor (or cancer potency factor)
    (mg/kg-day)-1
  • unit risk (mg/m3)-1 (inhalation, oral)

138
Toxicity Assessment Non-Carcinogenic Effects
Dose-Response Curve (non-carcinogenic effects)
LOAEL - Lowest Observed Adverse Effect
Level NOAEL - No Observable Adverse Effect
Level RfD - Reference dose
Response
X
RfD NOAEL LOAEL
Dose (mg/kg/day)
139
Toxicity Assessment Non-Carcinogenic Effects
  • Reference Dose NOAEL/(UF1 UF2 .... MF)
  • Uncertainty Factor(s) (UF) (uncertainty factor is
    set equal to 10)
  • account for variation in general population to
    protect sensitive subpopulation.
  • extrapolate from animals to humans to account for
    interspecies variability.
  • estimate a chronic NOAEL derived from a
    subchronic study.
  • estimate NOAEL from LOAEL.

140
Toxicity Assessment Non-Carcinogenic Effects
  • Reference Dose NOAEL/(UF1 UF2 .... MF)
  • Modifying Factor (MF) (ranges from gt 1 to 10 with
    a default of 1)
  • reflects a qualitative professional assessment of
    additional uncertainties in the study and in the
    entire database for the chemical(s) of concern
    and not explicitly addressed in the uncertainty
    factors.

141
Toxicity Assessment Carcinogenic Effects
Hypothetical Dose-Response Curve (carcinogenic
effects)
0.1



95 UCL

0.05
Occurrence of Cancer


0
0 500 1000 Human exposure
Animal experiments range range
Dose (mg/kg-day)
142
Toxicity Assessment Carcinogenic Effects
  • EPA Weight-of-Evidence Classification System for
    Carcinogenity

Group
Description
Examples
Human carcinogen, with sufficient evidence from
epidemiological studies
A
Benzene
B1 or B2
Probable human carcinogen B1 - with limited
evidence from epidemiological studies B2 - with
sufficient evidence from animal studies and
inadequate evidence or no data from
epidemiological studies
Benzo(a)pyrene
Possible human carcinogen, with limited evidence
from animal studies in absence of human data
C
PCE
Not classifiable as to human carcinogenicity,
owing to inadequate human and animal evidence
Ethylbenzene Toluene Xylenes
D
Evidence of noncarcinogenicity for humans, with
no evidence of
E
carcinogenicity in at least two adequate animal
tests in different
species or in both adequate animal and
epidemiological studies
143
Toxicity Assessment
  • Sources of toxicity information (in order of
    preference)
  • state specific toxicity values
  • Integrated Risk Information System (IRIS)
  • only RfDs and slope factors that have been
    reviewed by EPA.
  • no external peer review of safe dose estimates
    (RfDs, SFs).
  • EPA Criteria Documents
  • Health Effects Assessment Summary Tables (HEAST)
  • summarizes all toxicity data.
  • no internal or external peer review of quality of
    data.
  • Agency for Toxic Substances Disease Registry
    (ATSDR)
  • peer-reviewed literature

144
Toxicity Assessment
  • New directions
  • benchmark dose
  • mechanistic

145
Risk Characterization
  • Quantifying non-cancer effects
  • Quantifying cancer effects
  • Other considerations
  • cumulative risk/additive effects
  • addressing uncertainty and variability
  • synergistic effects

146
Risk Characterization
  • Quantifying cancer risks
  • estimated as the incremental probability of an
    individual developing cancer over a lifetime as a
    result of exposure to the potential carcinogen
  • IELCR Cancer Slope Factor x Lifetime Average
    Daily Dose
  • IELCR Individual Excess Lifetime Cancer Risk
  • Development of target risk is a policy decision

147
Risk Characterization
  • Quantifying non-carcinogenic effects
  • evaluated by comparing the estimated dose with
    the safe dose (reference dose or reference
    concentration).
  • ratio is called the Hazard Quotient (HQ)
  • HQ Intake / safe dose
  • Intake Applied Dose or Absorbed Dose
  • For single chemical evaluation, an HQlt1 means the
    chemical does not show an effect
  • Technical policy on additive effects of multiple
    chemicals

148
Example Quantifying Carcinogenic Risks
  • Residential drinking water

Exposure Concentration
Exposure Factors (Intake)
Toxicity (Slope Factor)
x
x

Health Risk
149
Example Quantifying Carcinogenic Risks
  • Intake Equation for Ingestion of Drinking Water

CW Concentration in Water of chemical of
concern (mg/l) IR Ingestion Rate (l/day) EF
Exposure Frequency (days/yr) ED Exposure
Duration (yr) BW Body Weight (kg) AT
Averaging Time (period over which exposure is
averaged) (days)
For noncarcinogens AT ED 365 days per year
and intake is called Chronic Daily Intake
(CDI). For carcinogens AT Lifetime (70 years)
365 days per year and intake is called Lifetime
Average Daily Dose (LADD).
150
Example Quantifying Carcinogenic Risks
  • Exposure Factors for ingestion of drinking water

Note value shown in parenthesis represents child
value a - 365 days per year x 70 year lifetime
151
Example Quantifying Carcinogenic Risks
  • Calculating concentration in ground water (Cw) -
    ground water ingestion

IELCR (Risk) Slope Factor (SF) x Intake
152
Class Exercise ?? Quantifying Carcinogenic Risks
  • An adult drinks water containing 0.05 mg/l
    benzene for 30 years.
  • estimate the Individual Excess Lifetime Cancer
    Risk
  • estimate the concentration of benzene that will
    result in an acceptable risk of 1 X 10-5

The slope factor for benzene is 2.90E-02
(mg/kg-d)-1
153
Deterministic Calculation
  • Probabilistic risk analysis (PRA) addresses both
    variability and uncertainty. Example
    Residential drinking water pathway

154
Deterministic Calculation Probabilistic Risk
Analysis Results
155
Risk-Based Decisions
  • Policy Decisions
  • how much risk is acceptable?
  • data quantity and quality
  • use of engineering/institutional controls
  • ecological receptors and habitats to be
    considered
  • Other Factors
  • economics, community issues, aesthetics

Risk Management
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