ASTM User Training in Risk-Based Corrective Action for Chemical Releases (Provisional ASTM Standard...

ASTM User Training

in

Risk-Based Corrective Action for Chemical Releases

(Provisional ASTM Standard Guide)

Day 1

6/1/99 ASTM RBCA for Chemicals User Training

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

– 8:00 - 8:30 Introduction– 8:30 - 9:30 Summarizing the Framework– 9:30 - 9:45 Break– 9:45 - 10:45 Summarizing the Framework– 10:45 - 11:00 Break– 11:00 -12:00 Technical Policy Decisions– 12:00 - 1:00 Lunch– 1:00 - 2:15 Technical Policy Decisions– 2:15 - 2:30 Break– 2:30 - 4:00 Developing the Site Conceptual Model– 4:00 - 4:15 Break– 4:15 - 5:00 Developing the Site Conceptual Model

Agenda: Day 1


7

Agenda - Day 2

– 8:00 - 9:30 RBSL/SSTL Development– 9:30 - 9:45 Break– 9:45 - 10:45 RBSL/ SSTL Development– 10:45 - 11:00 Break– 11:00 -12:00 RESC/SSEC Development/Data Collection– 12:00 - 1:00 Lunch– 1:00 - 2:30 Tier Decisions/Remedial Options– 2:30 - 2:45 Break– 2:45 - 4:00 Source Reduction/ Activity and Land Use Controls– 4:00 - 4:15 Break– 4:15 - 5:00 Factors for Consideration in Remedial Action Selection


8

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.

ASTM is an organization that has historically focused on promulgating standards for engineering tests and specifications for engineering materials.

Who is ASTM?


9

ASTM RBCA

Authored by a multi-functional and multi-disciplinary group of ASTM E-50 Subcommittee members, representing:

ASTM “RBCA”

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

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

Risk-Based Corrective Action (RBCA) Process


11

Why 3 Tiers (Levels) in RBCA?

Tier 1Tier 1

Tier 3Tier 3

TargetRisk

Every tier achieves the same level of public health protection

Tier 2Tier 2Less Site-Specific U

ncertainty

Greater Site-Specific Effort


12

Technical Policy Decisions

RBCA Framework Regulatory Program

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


13

RBCA Framework Regulatory Program


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


14

PolicyRBCA Customization: Technical Policy Decisions

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

Summarizing the Framework

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

Risk Toxicity & Exposure

Exposure Concentration & Intake

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


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

Step 1

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Step 8

Step 9

Step 10

ASTM Risk-Based Corrective Action (RBCA) Flowchart

YesNo

Initial Response Classification & Risk Reduction

Tier 1 Evaluation

Initial Site Assessment

Decision Point?

Interim Remedial

Action

Yes

Yes

No

Tier 2 Evaluation

No

NoNo

No

Yes

Yes

Yes

Tier 3 Evaluation

Yes

No

NoYes

Remedial Action Program

MonitoringNo

Further Action

NoYes

Yes

Yes

No

No

Decision Point?Decision Point?

Decision Point? Decision Point? Decision Point?

Decision Point? Decision Point?

Decision Point? Decision Point?

Decision Point?


22

Step 1


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

Step 1


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

Step 2

Ris

k

Initial Response Action

Initial Response Action& Risk Reduction

Risk Reductio

n Activity


25

Site Off-Site

Residual Phase

Source Area

Free Phase

Dissolved Phase

Free Phase

Vapor Phase

Vapor Phase

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

Step 1Initial Site Assessment Source(s) and Source Area(s)


26

Step 1

Atmospheric fate & transport

deposition

Site

Soil to Ground Water

Soil to air

Ground Water to Air

Ground Water Transport

Runoff

Dust to airOff-Site

Initial Site AssessmentTransport Mechanisms

Chemical(s) of concern dissolved in ground water


27

Initial Site AssessmentReceptors

Site Off-Site

Receptors

Step 1

Industrial land use Future land use ? Residential land use


28

Initial Site AssessmentRelevant 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

Step 1


29

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.

Step 1

Site

Point(s) of Exposure

Off-Site

Initial Site AssessmentPoint(s) of Exposure


30

Tier 1 EvaluationExposure Pathway

Receptor

Source Area

Transport Mechanism

Step 3

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 - 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

Leaching andGround Water

Transport


Transport

Wind Erosion and Atmospheric

Dispersion

Wind Erosion and Atmospheric

Dispersion

Residential Commercial/Industrial Construction worker Sensitive habitat

PRIMARY SOURCES

SECONDARYSOURCES

EXPOSUREROUTES

RECEPTORSTRANSPORT

MECHANISMS

AffectedSubsurface

Soils (>3 ft

depth)

AffectedSubsurface

Soils (>3 ft

depth)

Stormwater/SurfaceWater

Transport


Transport

SURFACE WATER Recreational Use/Sensitive Habitat

SURFACE WATER Recreational Use/Sensitive Habitat

Volatilizationand

AtmosphericDispersion

Volatilizationand


Ground WaterPotable Water UseProcess Water Use

AIR Inhalation of Vapor

or Particulates

AIR Inhalation of Vapor

or Particulates

SOILDermal Contact

or Ingestion

SOILDermal Contact

or Ingestion

Product Storage Piping / Distribution Operations Waste Management Unit Other

Product Storage Piping / Distribution Operations Waste Management Unit Other

Volatilizationand Enclosed

Space Accumulation


Space Accumulation

Mobile Free

Liquid Migration

Mobile Free

Liquid Migration

DissolvedGround WaterPlume

DissolvedGround WaterPlume

AffectedSurface Soils,Sediments or Surface Water


Free-PhaseLiquidPlume

Free-PhaseLiquidPlume

AffectedSurface

Soils (<3 ft

depth)

AffectedSurface

Soils (<3 ft

depth)

Residential Commercial/Industrial Construction worker

Residential Commercial/Industrial

Residential Recreational Sensitive habitat

Step 3

Site Conceptual Model


32

RBSLs

c

o soil o d i air

g

kg soil

TR BW ATdays

years

SFkg

mgIR RAF SA M RAF SF IR VF EF ED

365

10 6sinh

Step 3

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

Step 3


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

Step 3


35

SiteOff-Site

Tier 1 EvaluationRisk-Based Screening Levels

CRBSL

CRBSL

CRBSL

CRBSL

CRBSL

CRBSL

CRBSLPoint(s) of exposure is assumed to be located proximal to the source area(s)

Compare highest concentrations of chemical(s) of concern to RBSL for complete and potentially complete exposure pathways

Compare site conditions to RESC

Step 3


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

Step 4


37


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.

Step 4


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.

Step 4


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

Step 4


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.

Step 4


41

Tier 2 SSTL Step 5

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

Step 5


43

Example Tier 2 Evaluation

Substituting site-specific parameters in RBSL method

Step 5

CGW

CW

1

1 V GW

I W

W = source width parallel to ground water flow [m]

GW = 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]

W

I

V GW

CW


44


Statistical representation of source area concentrations

Step 5


45

SiteOff-Site

Cpoe

Csoil

Cgw


Site-Specific Target Level Applied at Source Area

RBSL Applied at Point of Exposure

Source Area

Step 5

Back-calculating SSTL at source area(s) by applying RBSL at point of exposure


46


Back-calculating SSTL at source area(s) by applying RBSL at point of exposure

Step 5

Cgw(x) = C f (degradation, seepage velocity, thickness of source zone, dispersion)

Cgw = chemical of concern along centerline of the plumeCsteady state source concentration


47


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

Step 5


48

SiteOff-Site

Cpoe

Csoil

Cgw

Tier 2 - Point(s) of Demonstration

Source Area

Step 5

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).

Cpod


49

Step 6


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

Step 6


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

Step 6

Tier 2 Outcomes


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

Step 6

Tier 2 Outcomes



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

Step 7

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

Step 7


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

Step 7


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

Step 7


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

Step 8

Tier 3 Outcomes


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

Step 8

Tier 3 Outcomes




59

Step 9

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

Step 9

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

Considerations: source removal or reduction eliminate exposure natural attenuation engineering controls institutional controls

Weight of considerations are based on a technical policy decision

Step 9


62

Step 10

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

Step 10


RBCA: How to Implement a Program


65


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 and Policy Decisions

Political and

SocialEconomic

Scientific

Regulatory DrivenDecisions made as part of a regulatory program that

apply to all sites or a set of circumstances

Site DrivenDecisions made at an

individual site based on site-specific circumstances

Business DrivenDecisions 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 InvolvementProgram 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 DecisionGround 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 DecisionGround 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

High Uncertainty&

Conservatism

Low Uncertainty&

Conservatism

Tier 3 Tier I

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


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


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


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 RiskTarget Risk Levels

USEPA excess lifetime cancer risk range– EPA’s 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

Background Risk: Existing risk of cancer incidence.

Excess Risk: Additional risk of cancer incidence due to exposure to site constituents.

BackgroundCancer Risk

ExcessRisk Limit Total Risk

0.25 1.0E-6 0.250001

0.25 1.0E-5 0.25001

0.25 0.25011.0E-4

Cancer RiskExcess vs. Total Cancer Risk


97

Cumulative Cancer RisksExample

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-CancerHazard 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

= Risk for a single chemical in Tier 1

= Risk of all chemicals in Tier 3

Additive Non- Cancer RisksExample


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


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


Individual versus a population/community– individual considered only when rare, threatened or

endangered species are involved– population/community is usually what is considered


106


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

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

Receptors:

• Residents

• Commercial or Industrial

workers

• Construction workers

• Recreational Users

• Relevant Ecological

Receptors and Habitats

PRIMARY SOURCES

SECONDARY SOURCES

EXPOSUREROUTES RECEPTORS

TRANSPORTMECHANISMS

AffectedSub-surface

Soils (> 3 ft depth)

Sources:

• Product Storage

• Piping/Distribution

• Operations

• Waste Mgmt Units

• Other

Above Ground Storage Tank Piping

Leaching andGround WaterTransport

GROUND WATER

Potable Water Use

Commercial or Industrial Workers

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

Exposure Pathway

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


Initial SCM Risk-based Decision• Remedial Action• Collect Additional data• Tier upgrade

Refined SCM

Site Conceptual Model Development

Working hypothesis of site management needs– Updated as new data become available

Valuable communication tool


114

Source/Source Area – a source and mechanism for chemical release

into the environment– physical/chemical, toxicological properties

Source

Source

Sources, Transport Mechanisms and Receptors


115

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)

Tra

nsp

ort

Transport



116



117

Receptor


Based on reasonable potential current & future land and water use

– residents - visitors– relevant ecological receptors & habitats– reasonable potential future receptors


118


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

Receptor


119


Relevant ecological receptors and habitats

– identify specifies and habitats– develop exposure scenarios– how do we identify?

Receptor


120

Example of a conceptual model

Surficial Soil

Potential Receptors

Future Land UseCurrent Land Use

On-Site

Volatilization/Vapor Migration



Non-AqueousPhase Liquid

DissolvedPhase

Subsurface Soil

Res

iden

ts

Vis

itors

/Oth

er

Com

mer

cial

/Ind

ustr

ial

Wor

kers

Com

mer

cial

/Ind

ustr

ial

Wor

kers

Res

iden

ts

Con

stru

ctio

n W

orke

rs

Res

iden

ts

Vis

itors

/Oth

er

Con

stru

ctio

n W

orke

rs

Com

mer

cial

/Ind

ustr

ial

Wor

kers

Vis

itors

/Oth

er

Con

stru

ctio

n W

orke

rs

Off-SiteOn-SiteOff-Site

TransportMechanisms

ExposureRoute

SecondarySources

Con

stru

ctio

n W

orke

rs

Res

iden

ts

Com

mer

cial

/Ind

ustr

ial

Wor

kers

Vis

itors

/Oth

er


Inhalation (Enclosed Space)

Inhalation (Ambient/Outdoor)


Dermal Contact



Dermal Contact



Ingestion

Ingestion (Potable Water)

Ingestion (Non-Potable Water)

Dermal Contact



Wind Erosion/Dispersion

Potentially Completed Pathway - SSTL Calculated


121

Chemical Storage Piping / Distribution Operations Waste Management

Unit Soil or Waste Piles Lagoons or Ponds Other

ResidentialResidentialCommercial/IndustrialCommercial/IndustrialConstruction workerConstruction workerRelevant Ecological Relevant Ecological ReceptorReceptor

ResidentialResidentialCommercial/IndustrialCommercial/IndustrialConstruction workerConstruction worker

ResidentialResidentialCommercial/IndustrialCommercial/Industrial

RecreationalRecreationalRelevant Ecological Relevant Ecological ReceptorReceptor

PRIMARY SOURCES

SECONDARYSOURCES

EXPOSUREROUTES

RECEPTORSTRANSPORTMECHANISMS

AffectedSubsurface

Soils (>3 ft depth)


Transport

SURFACE WATERRecreational Use/Relevant Habitat

Volatilizationand


GROUND WATERPotable Water Use

AIRInhalation of Vapor

or Particulates

SOILDermal Contact

or Ingestion

AffectedSurface

Soils (< 3 ft depth)

Wind Erosion and Atmospheric Dispersion


Space Accumulation

Mobile NAPL

Migration

DissolvedGround Water

Plume


Transport


Non-Aqueous Phase Liquid

(NAPL)

ResidentialResidential

Relevant Ecological Relevant Ecological ReceptorReceptor

Example of a conceptual model (ASTM PS-104-98)


122

Scenario Medium Exposure Exposure Receptor Receptor ExposureOn-Site/

Type ofRationale for Selection or

Exclusion

Timeframe Medium Point Population Age RouteOff-Site

Analysis of Exposure Pathway

Current Ground WaterGround Water

Aquifer 1-- Tap Water

Resident Adult DermalOff- Site

QuantResidents currently live next to the

site, and their wells draw from Aquifer 1.

IngestionOff- Site



Child DermalOff- Site



IngestionOff- Site



Trespasser/ Adult DermalOn-Site

NoneNo groundwater seeps or wells on

site.

Visitor IngestionOn-Site


site.

Child DermalOn-Site


site.

IngestionOn-Site


site.

AirAquifer 1--

Water VaporsResident Adult Inhalation

Off-Site



at showerhead

Child InhalationOff-Site

NoneChildren are assumed not to

shower.

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

ExposureExposureConcentrationConcentration

xxExposureExposureFactorsFactors

== Health RiskHealth Riskxx ToxicityToxicity

Target Level Calculation

Risk Estimation


126

Assessing risk along a pathway

Source

Conceptual Model

Tra

nsp

ort

SourceConcentrations

Risk Estimation

ExposureConcentrations

Dose

HealthRisk


AllowableRisk

AllowableSource

Concentrations

Receptor


127

More site-specific

Each step uses a Model

Less site-specific

Components of risk assessment

Fate & Transport

Exposure

Toxicity

Dose


HealthRisk



128

Risk Characterization

Dose-Response

Assessment

Exposure Assessment

Transport Assessment

Source Characterization

Fate &Transport Exposure Toxicity

HealthRisk



Dose

Risk Assessment Process


129

RESEARCH RISK ASSESSMENT

RISK MANAGEMENT

Understanding the mechanistic linkages between:

SourcesExposureDoseResponse

(1) Hazard Identification

(2) Exposure Dose Response Assessment(3) Exposure Assessment

(4) Risk Characterization

(5) Identification of Research Needs

Risk Management Options

Public Health, Economic, Social, Political Consequences of Options

Risk Management Decisions and Actions

Adapted from “Science and Judgement in Risk Assessment”, NRC, 1994

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

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

Risk Management under RBCA


133

Transport

Exposure AssessmentData 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

Transport

Source

Exposure Assessment Sources

Chemicals of concern– e.g., physical, chemical, toxicological

Representative concentration Physical setting

– e.g., soil characteristics, hydrogeology, climate


135

Transport

Exposure AssessmentFate & 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

Exposure AssessmentOther 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

ToxicityToxicity 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

Dose-Response Curve (non-carcinogenic effects)

RfD NOAEL LOAEL

Dose (mg/kg/day)

% R

espo

nse

LOAEL - Lowest Observed Adverse Effect Level

NOAEL - No Observable Adverse Effect Level

RfD - Reference dose

X

Toxicity AssessmentNon-Carcinogenic Effects Toxicity


139

Toxicity

Toxicity AssessmentNon-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

Toxicity AssessmentNon-Carcinogenic Effects

Reference Dose = NOAEL/(UF1 * UF2 * .... * MF)– Modifying Factor (MF) (ranges from > 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

Hypothetical Dose-Response Curve

(carcinogenic effects)

0 500 1000| Human exposure | | Animal experiments range | range

Dose (mg/kg-day)

0

0.05

0.1***

*

*

*

95% UCL

Occ

urre

nce

of C

ance

rToxicity AssessmentCarcinogenic Effects Toxicity


142

Toxicity

Toxicity AssessmentCarcinogenic Effects

EPA Weight-of-Evidence Classification System for Carcinogenity

Group Description Examples

A Human carcinogen, with sufficient evidence from epidemiological studies 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

C Possible human carcinogen, with limited evidence from animal studies in absence of human data

PCE

D Not classifiable as to human carcinogenicity, owing to inadequate human and animal evidence

EthylbenzeneTolueneXylenes

E Evidence of noncarcinogenicity for humans, with no evidence ofcarcinogenicity in at least two adequate animal tests in differentspecies or in both adequate animal and epidemiological studies


143

ToxicityToxicity 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

Toxicity


145

RiskRisk Characterization

Quantifying non-cancer effects Quantifying cancer effects Other considerations

– cumulative risk/additive effects– addressing uncertainty and variability– synergistic effects


146


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


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 HQ<1 means the chemical does not show an effect

– Technical policy on additive effects of multiple chemicals


148

ExposureExposureConcentrationConcentration

xx ExposureExposureFactors (Intake)Factors (Intake)

== Health RiskHealth Riskxx ToxicityToxicity(Slope Factor)(Slope Factor)


Example Quantifying Carcinogenic Risks

Residential drinking water


149

Intake (mg/kg-day) = CW x IR x EF x ED

BW x AT

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).


Intake Equation for Ingestion of Drinking Water


150


Parameter Definition Units RME MLE

BWa Body Weight, Adult kg 70 70

BWc Body Weight, Child kg 15 15

ATc Averaging time (Cancer) days 25550a 25550a

ATnc Averaging Time (non-Cancer)

days ED x365d/y

ED x365d/yIRwr Drinking water ingestion -

res.l/day 2 1.4

EFr Exposure frequency -resident

day/yr 350 274

EDr Exposure duration -residential

years 30 (6) 8 (6)

Note: value shown in parenthesis represents child valuea - 365 days per year x 70 year lifetime

Exposure Factors for ingestion of drinking water


151

IELCR (Risk) = Slope Factor (SF) x Intake

Cw = Risk x BW x AT SF x ED x EF x IR

Risk = SF x CW x IR x EF x EDBW x AT


Calculating concentration in ground water (Cw) - ground water ingestion


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

Factor Typical Point

Value Distribution Mean Range

Days at Homeper Year (days/yr) 350 351 323 - 365

Years at Home(yrs)

30 8 1 - 50

Ingestion Rate (L/day)

2 1.4 0.1- 4

Body Weight (kg)

70 71 32 - 115

Deterministic Calculation

Probabilistic risk analysis (PRA) addresses both variability and uncertainty. Example: Residential drinking water pathway


154

Concentration (ppm)0.00 0.04 0.08 0.12 0.16

Forecast: Residential Drinking Water Pathway

Mean = 0.03 ppm

Point Estimate = 0.002 ppm95th Percentile = 0.002 ppm

Median = 0.01 ppm

Risk Level =10 -6

Pro

babi

lity

Deterministic Calculation Probabilistic Risk Analysis Results


155

Risk Management

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

Transport

Date post:	29-Dec-2015
Category:	Documents
Upload:	ruby-patterson
View:	225 times
Download:	8 times