ASTM User Training

1
ASTM User Training

• in
• Risk-Based Corrective Action for Chemical
  Releases
• (Provisional ASTM Standard Guide)
• Day 2

2
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

3
RBSL Development
4
RBSL Development

• Acceptable concentrations of chemical(s) of
  concern developed for the Tier 1 evaluation
• conservative/non-site-specific models and input
  values
• data collection biased to area of highest
  concentration

5
RBSL Development Components of Risk Assessment
Health Risk
Toxicity
Dose
Exposure
Exposure Concentrations
Fate Transport
Source Concentrations
6
RBSL DevelopmentSite Conceptual Model

• Develop a generic or site-specific site
  conceptual model to identify the RBSL to be
  determined
• site conceptual model can be either program or
  site-specific based
• program based RBSL
• generic exposure pathways
• non-site specific/conservative parameters
• individual site based RBSL
• site-specific exposure pathways
• non-site specific/conservative parameters

7
RBSL DevelopmentExposure Pathway Considerations

• Receptors
• residential adult or children, worker
• Transport mechanisms
• soil to ground water leaching
• soil and ground water to indoor or outdoor air
• Exposure routes
• ingestion
• inhalation
• dermal contact

8
RBSL DevelopmentUncertainty

• Define the uncertainties and the approach for
  addressing
• algorithm
• simple partitioning?
• heterogeneity of subsurface environment
• conservative soil type?
• biodegradation
• ignore?

9
RBSL DevelopmentMethods and Parameters

• Identify the methods that are to be used to
  calculate the RBSL so that they are reproducible
• simple algorithms
• analytical models
• Define the parameters that are required by the
  algorithms or models used to calculate the RBSL
• fate and transport
• chemical and site characteristics
• toxicity
• exposure

10
Fate and Transport ParametersChemical
Characteristics

• Molecular weight
• Solubility
• Vapor pressure
• Henrys law constant
• Soil-water partitioning coefficient
• Octanol/water coefficient
• Degradation rate
• Air diffusivity
• Water diffusivity

11
Fate and Transport ParametersSite Characteristics

• Saturated Zone
• Groundwater mixing zone thickness
• Width of source area
• Depth of source area

• Vadose Zone
• Lower depth of surficial soil
• Thickness of capillary fringe
• Thickness of vadose zone
• Depth to groundwater
• Depth to top of subsurface soil sources
• Depth from bottom of subsurface sources to ground
  water

12
Fate and Transport ParametersSite
Characteristics - Saturated Zone

• Groundwater Darcy and seepage velocity
• Fraction organic carbon
• Ground water gradient
• Saturated hydraulic conductivity
• Soil porosity
• Soil bulk density
• Dispersivity
• longitudinal, transverse, vertical

13
Fate and Transport ParametersSite
Characteristics - Vadose Zone

• Fraction organic carbon
• Infiltration rate
• Volumetric air content in capillary fringe soils
• Volumetric water content in capillary fringe
• Volumetric air content
• Volumetric water content
• Soil porosity
• Soil bulk density

14
Fate and Transport ParametersSite
Characteristics - Volatilization

• Enclosed-space air exchange rate
• Enclosed-space volume to infiltration area ratio
• Enclosed-space foundation or wall thickness
• Areal fraction of cracks in foundations/walls
• Vol. Air content in foundation/wall cracks

• Vol. Water content in foundation/wall cracks
• Particulate emission rate
• Wind speed above ground surface in ambient mixing
  zone
• Width of source area parallel to wind flow
• Ambient air mixing zone height
• Averaging time for vapor flux

15
Toxicity Parameters

• Target risk
• Hazard quotient
• Chemical toxicity
• slope factor (mg/kg-day)-1 or unit risk factor
  (mg/m3)-1
• ingestion
• inhalation
• reference dose (mg/kg-day) or reference
  concentration (mg/m3)
• ingestion
• inhalation

16
Exposure Parameters

• Averaging time
• cancer
• non-cancer
• Body weight
• Exposure duration
• Exposure frequency
• Exposure time for indoor air
• Exposure time for outdoor air
• Soil ingestion rate

• Daily indoor inhalation rate
• Daily outdoor inhalation rate
• Daily water ingestion rate
• Soil to skin adherence factor
• Skin surface area for soil exposure

17
RBSL DevelopmentOther Relevant Measurable
Criteria

• Concentrations of chemical(s) of concern, other
  numeric values, physical condition or performance
  criteria, other than the RBSL, RESC, SSTL,SSEC,
  used to define corrective action goals
• consistent with the technical policy decisions
• regulatory standards
• consensus criteria
• aesthetic criteria
• groundwater protection criteria

18
Ground Water Ingestion

• Calculate (see Class Exercise ?)
• Other relevant measurable criteria (ORMC)
• e.g., drinking water maximum contaminant levels
  (MCL)

Non-Cancer
Cancer
SF Cancer Slope Factor (mg/kg-day)-1 HQ
Hazard Quotient RfD Reference Dose
(mg/kg-day) 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)
19
Leaching from Source Area to Ground Water

• Tier 1 RBSL are based on conservative default
  parameters
• steady state
• infinite source
• no vapor loss
• no biodegradation
• no dispersion/diffusion
• RBSLgw RBSLdw

RBSLs-gw
RBSLgw
20
Leaching from Source Area to Ground Water
Partition Factor
Attenuation Factor
Back Calculate To Soil Concentration
21
Leaching from Source Area to Ground Water -
Attenuation Factors
Attenuation (neglecting biodegradation) is
controlled by physical site parameters and the
infiltration rate.
22
Leaching from Source Area to Ground Water -
Partitioning Factors
Concentrations of chemicals of concern measured
in soil includes chemical mass that is
volatilized into soil gas, dissolved into pore
moisture, and sorbed onto the soil surface.
Controlled by Chemical and Soil Parameters
23
Class Exercise ??Soil to Ground Water Leaching

• MEK
• chemical characteristics
• physical parameters
• ground water RBSL
• unsaturated zone parameters
• algorithms
• uncertainty

24
Direct Contact -Carcinogens
Ingestion of soil

• Ingestion of soil
• Inhalation of vapor and particulates
• Dermal contact with soil

Dermal Contact
Inhalation of particulates
Inhalation of vapors
IRsoil ingestion rate of soil FI fraction
ingested IRair inhalation rate of
air RAFd Dermal relative absorption factor SA
Skin surface area (cm2/day) M Soil
to skin adherence factor (mg/cm3) VF
Volatilization factor
25
Direct ContactVolatilization Factors

• Volatilization factor VFss for Surficial Soil
  Ambient Air Vapors

• Volatilization factor VFr for Surficial Soil
  Ambient Air Particulates

Pe particulate emission rate (g/cm-s) W
width of source are parralell to the wind
(cm) Uair wund speed in ambient mixing zone
(cm/s) dair ambient air mixing zone (cm) rs
soil bulk density (g-soil/cm3-soil) d lower
depth of surficial zone
26
Direct ContactAlgorithms
Cancer RBSLs (ug/kg)
Non-Cancer RBSLs (ug/kg)
27
Class Exercise ??Direct Contact

• Mercury
• chemical characteristics
• physical parameters
• target risk/hazard quotient
• exposure factors
• unsaturated zone parameters
• algorithm
• uncertainty

28
Vapor Intrusion into Buildings

• Evaluation in Tier 1 is very conservative
• Often a significant pathway

Mixing in breathing zone
Diffusive transport to breathing zone
Impacted soil and/or ground water in equilibrium
with soil gas
29
Vapor Intrusion into BuildingsVolatilization
Factor
H Henrys law constant dair ambient air
mixing zone (cm) rs soil bulk density
(g-soil/cm3-soil) qas volumetric air content in
vadose zone (cm/cm) Kd soil-water sorption
coefficient (g/g) Ls depth to subsurface soil
source (cm) LB enclosed space
volume/infiltration area ratio (cm/cm) Lcrack
enclosed space foundation or wall thickness
(cm) ER enclosed space air exchange ratio
(L/s) h areal fraction of cracks in
foundation/walls (cm2/cm2) Deffs effective
diffusion coefficient in soil based on vapor
phase (cm2/s) Deffcrack effective diffusion
coefficient through cracks (cm2/s)
30
Vapor Intrusion Into Buildings Controlling
Parameters

• Soil to Soil Vapor Partitioning
• Kd f(foc, koc)
• chemical Henrys Constant and Solubility
• existence of a NAPL
• Diffusive Transport
• Deff f(qws, qwa)
• layering in the vadose zone
• Indoor Air Transport
• building construction

31
Equilibrium Partitioning Example
100
Linear Partitioning Approximation
Benzene Concentration in Ground
Water Cw (mg-benzene/l-water)
Raoult's Law Limit
10
Expected concentration
1
100
10000
1000
Residual Gasoline Concentration in Soil
CT (mg-gasoline/kg-soil)
Cwmax xiSi xi mole fraction of benzene Si
solubility of benzene
32
Class Exercise ??Ground Water to Indoor Air

• Tetrachlorethene
• chemical characteristics
• physical parameters
• indoor air RBSL
• saturated zone parameters
• unsaturated zone parameters
• heterogeneity of soils
• biodegradation
• algorithms
• uncertainty

33
Class Exercise ??Cumulative Risk

• Show the comparison of a few chemicals to the
  their RBSLs
• Show the ratios of the concentrations to the
  RSBLs
• Discuss apportioning the target risk among the
  chemicals to address cumulative effects
• Texas is an example (may be too complicated)
• more than 10 chemicals that are carcinogens or 10
  non-carcinogens with the same target organ, then
  adjust the RBSL
• 10gt sum for all i (RBSLadj-i /RBSL)

34
SSTL Development
35
SSTL DevelopmentSite Specific Parameter Values

• When should site-specific data be considered?
• Which parameters should be considered for each
  exposure pathway?
• How should site specific data be collected and
  analyzed (recommended methods)?
• What is the reasonable range of values for each
  site-specific parameter?

36
SSTL DevelopmentSite Specific Parameter Values

• Statistical representation of source area
  concentrations of chemical(s) of concern,
• Default parameter values used to develop the RBSL
  are not appropriate for site-specific conditions,
  or
• The RBSL is applied at a site-specific point of
  demonstration to develop SSTL

37
SSTL DevelopmentSite Specific Parameter Values

• Site specific parameters can have a large impact
  on calculated SSTL as compared to RBSL
• Sometimes more than an order of magnitude!

38
SSTL DevelopmentSite Specific Parameter Values

• Examine importance of parameters by looking at
  exposure pathways
• source composition
• NAPL composition, molecular weight, density,
  total volume, component effective solubility
• soil properties
• total and effective porosity, moisture content,
  organic carbon fraction, and soil permeability or
  hydraulic conductivity
• physical site conditions
• depth from source to groundwater, thickness of
  vadose zone, thickness of capillary fringe,
  infiltration rate
• ground water flow
• site specific aquifer data, hydraulic
  conductivity, hydraulic gradient
• building design
• Air exchange rate, building dimensions,
  foundation construction

39
SSTL Development - ExampleEffective Solubility
Limit (Seff)

• Estimated based on Raoults Law using published
  references for the pure component solubility
  limit (e.g., see Montgomery and Welkom, 1990)
• data on the mole fraction of compounds in
  gasoline can be found in published references
  (e.g., see Johnson et al, 1990) or measured in a
  sample of source zone soil.

40
SSTL DevelopmentHeterogeneous Soils

• Will heterogeneous soil properties limit flux?
• define the effective diffusion coefficient, Deff

Homogeneous layer
Heterogeneous soil layers
1
Deff
DTeff, L
2
3
41
SSTL DevelopmentHeterogeneous Soils

• How does moisture content affect diffusion?

Total Porosity
H0.22 DH2O / Dair 0.0001
42
SSTL DevelopmentHeterogeneity Summary

• Zones of low Deff will reduce flux and increase
  SSTL
• Can result in an order of magnitude change in
  SSTL
• Estimation methods for Deff
• typical properties for soil types
• site specific soil property analysis
• in-situ measurement of Deff

43
SSTL DevelopmentBiodegradation

• Aerobic Biodegradation
• Oxygen acts as an electron acceptor.
  Indigenous micro-organisms exist that are capable
  of degrading many volatile organic compounds.
  The most significant rates of degradation occur
  aerobically
• Field studies conducted to date indicate that the
  factor that most significantly controls
  biodegradation in subsurface environments is the
  rate of oxygen transport.
• Anaerobic Biodegradation
• Oxygen acts as an electron acceptor. There are
  other potential electron acceptors commonly found
  in aquifer environments, including NO3-2, SO4-2,
  Fe3.

44
SSTL DevelopmentBiodegradation

• For mathematical simplicity, most volatile
  organic chemical degradation reactions are
  treated as being first-order reactions. In
  other words

concentration of chemical
is proportional to
decay rate
dC
?
?
?
C
dt
45
SSTL DevelopmentBiodegradation - Decay

• The concentration can be determined by
• C(t) Co exp (-?t)
• ln(C(t)/Co) -?t
• ? first order decay rate constant (t-1)
• C(t) concentration at time t (mg/l)
• Co initial concentration (mg/l)

For example, typical values for the rate constant
(?) for benzene fall in the range 0.1 - 1 per
day.
46
SSTL DevelopmentBiodegradation - Decay

• The half-life of a chemical is defined as the
  time it takes for the first-order reaction to
  transform half of the initial mass of the
  chemical. If C(t)/Co is replaced with 0.5, then
• t0.5 (ln 2)/? or t0.5 0.693/?
• t0.5 half-life of the chemical (days)

47
SSTL DevelopmentBiodegradation

• Illustration of first-order decay

48
SSTL Development Natural Attenuation

• Natural Attenuation refers to the reduction in
  mass, mobility, or concentration of chemical(s)
  of concern by intrinsic processes (e.g.,
  advection, dispersion, diffusion, dilution,
  sorption, degradation).
• Dilution Attenuation Factor (DAF)

Data collection needs include flow direction
gradient hydraulic conductivity lithology
depth to ground water ground water
fluctuations extent of source historical
monitoring data
49
SSTL Development Using RBSL Algorithms

• Default parameter values used to develop the RBSL
  are not appropriate for site-specific conditions
• RBSL algorithms and Tier 1 point(s) of exposure
  are appropriate for the site

50
Class Exercise ?? Using RBSL Algorithms

• Example problem
• substituting site-specific values to calculate
  SSTL
• use ground water to indoor air
• parameters
• depth to ground water
• soil moisture content
• sensitivity

51
SSTL DevelopmentStatistical Representation

• 95 UCL of arithmetic mean
• sufficient number and quality of samples to
  derive normal, log-normal or other applicable
  frequency distribution
• Based on appropriate statistical methodology for
  normal or log-normal distributions

52
Class Exercise ??Statistical Representation

• Example problem
• soil concentrations
• use direct contact RBSL
• compare highest value to average values
• look at area weighted averages
• look at histograms translate to frequency
  distributions
• calculate the probability of the concentration
  being above the RBSL based on the distribution

53
SSTL Development Using Exposure Pathway
Evaluation
Receptor
Transport
Source
Conceptual Model
54
SSTL Development Using Exposure Pathway
Evaluation
3
SSTL Applied at Source Area
RBSL or ORMC Applied at Point of Exposure
Source Area
Csoil
Cgw
Cpoe
1
2
Back-calculating site-specific target levels at
source areas
55
SSTL Development Using Exposure Pathway
Evaluation

• Allowable concentration at the point(s) of
  exposure (CPOE) is based on
• RBSL,
• ORMC, or
• SSTL calculated using target risk, toxicity
  factors and site-specific exposure factors

56
SSTL Development Using Exposure Pathway
Evaluation

• Allowable concentration in ground water at the
  source area (Cgw) is
• An attenuation factor (AF) of less than 1 is a
  result of
• diffusion
• dispersion
• adsorption
• decay (chemical and biological)

57
SSTL Development Using Exposure Pathway
Evaluation

• Allowable concentration in soil at the source
  area (Csoil) is
• A leaching factor (LF) of less than 1 is a result
  of
• diffusion
• dispersion
• adsorption
• decay (chemical and biological)

58
Using Ground Water Transport Modeling to Develop
the AFConsiderations and Data Requirements

• Source-specific data
• size, shape strength
• type of source
• continuous, constant pulse, exponentially
  decaying
• Receptor-specific data
• distance orientation relative to source
• Chemical-specific data
• persistence, mobility, solubility
• concentration in source area

• Media-specific data
• aquifer characteristics
• porosity, hydraulic conductivity
• Model applicability
• simplest model to represent transport
• does it apply?

59
Conceptual Ground Water ModelSignificant
Transport Processes

• Different processes to consider

Infiltration from Rainfall
COC in Soil
Aqueous Advection
Advection and Dispersion In Groundwater
60
Ground Water Transport ModelingDomenico Solution

• Transport processes
• dispersion in 3 dimensions
• one-dimensional uniform advection
• Model assumptions and applicability
• one-dimensional flow and 3-dimensional dispersion
• first-order decay rate based on dissolved and
  adsorbed phases decaying at the same rate
• medium is isotropic and homogeneous
• source concentration is constant
• areal source perpendicular to the direction of
  flow

61
Ground Water Transport ModelingDomenico

• Analytical solution for the steady-state
  concentration along the centerline

62
Ground Water Transport ModelingDomenico

• Analytical solution, steady-state
• Attenuation factor relates the concentration at
  the source to the centerline down gradient
  concentration at the water table
• Function of
• advection and partitioning vKi/qR
• decay
• dispersion longitudinal, transverse and vertical
• source area depth and width

63
Ground Water Transport Modeling
Steady-state centerline concentrations predicted
by the Domenico solution
k0.0/d
k0.1/d
k1.0/d
Source width 50 ft source thickness 5 ft GW
velocity 0.3 ft/d ?x 0.1 L ?y ?x/3 ?z
0.035 ?x
no decay
C(x)/C(source)
max decay
Distance from Source ft
64
Transport ModelingCaution

• Given the inherent limitations (data, model
  assumptions), models are used to estimate rates
  of transport, expected trends in data. This
  information is very useful in developing SSTL,
  monitoring plans and remedial designs, and for
  assessing the significance of various exposure
  and transport pathways. Models should not be a
  substitute for site-specific data. Model
  results are only one of the elements used in
  making RBCA decisions!!!

65
Transport ModelingSummary

• Identify the processes to considered in the
  modeling
• Determine the assumptions made by the model
• Identify the appropriate data requirements
• balance the model complexity with the available
  data
• Verify the model predictions with empirical data

66
Class Exercise ?? Using Exposure Pathway
Evaluation

• Move point of demonstration to calculate new
  concentration of chemical(s) of concern in ground
  water at the source area
• Domenico
• Calculate concentration in soil at the source
  area
• use soil to ground water leachate RBSL calculation

67
RESC/SSEC Development
68
Example 1 City Service Center

• A service station in the downtown of a city has
  experienced a release from an underground storage
  tank.
• Chemical(s) of concern associated with gasoline
  have been identified in the underlying soils and
  groundwater.
• The city service station is not located near
  relevant ecological receptors or habitats.

69
Example 1 City Service CenterInitial Site
Assessment

• No ecological relevant receptors or habitats have
  been identified
• these conditions were documented
• Ecological issues need not be considered
• Initial site assessment is sufficient

70
Example 2 Rural Manufacturing Facility

• A manufacturing site located in a rural area has
  observed concentrations of TCE in its soils and
  ground water
• The site is located near a small river, which
  provides habitat for aquatic biota but is not
  used for drinking water
• The groundwater flow is toward the river
• It is likely that the groundwater discharges to
  the river.

71
Example 2 Rural Manufacturing Facility -
Initial Site Assessment

• Potentially complete pathways and exposure to
  relevant ecological receptors and habitats exist.
• Proceed to Tier 1 assessment

72
Example 2 Rural Manufacturing Facility - Tier 1

• Probability of potentially complete pathways and
  exposure to relevant ecological receptors and
  habitats has increased, but is not conclusively
  known.
• Concentrations of TCE in ground water range from
  70 1,200 ?g/l
• Concentrations of TCE in the surface water are
  above the generic screening levels
• attributed directly to the presence of a hot
  spot.

73
Example 2 Rural Manufacturing Facility - Tier 2

• The concentrations of TCE in the surface water
  that are above the generic screening levels were
  attributed directly to the presence of a hot
  spot
• Exit Tier 2 and proceed to remedial action

74
Example 3 Printing Site

• The Printer is located near a wetland and river
• Drainage and runoff from the Printing Site are
  believed to have contributed to elevated
  concentrations of organic chemicals and metals in
  a nearby swamp.

75
Example 3 Printing SiteInitial Site Assessment

• Elevated concentrations of organic chemicals and
  metals are known to exist in the swamp area
• Proceed to Tier 1 based upon
• potentially completed exposure pathways and
• the presence of relevant ecological receptors and
  habitats

76
Example 3 Printing SiteTier 1

• Runoff could carry chemical(s) of concern from
  the spill locations to the wetlands
• Concentrations of several organic chemicals and
  metals are above the surface water screening
  levels
• Proceed to Tier 2 to refine generic criteria to
  more site specific values

77
Example 3 Printing SiteTier 2

• Concentrations of several organic chemicals and
  metals in soil and wetland sediment at the site
  are above those in the region for several metals
• The site also exceeds ecological toxicological
  benchmarks.
• Proceed to a site-specific Tier 3 evaluation

78
Data Collection
79
Data Collection

• Follows line of evidences
• background information
• qualitative data
• quantitative data
• Purpose and use
• Analytical methods
• Quantity and quality necessary to make decisions
• conservatism vs. uncertainty
• technical policy decisions

80
Data CollectionTier 1

• Objective is to demonstrate highest concentration
  of chemical(s) of concern
• for each exposure pathway identified
• Drivers
• site conceptual model
• concentrations of chemical(s) of concern
• Technical policy decisions
• what quantity and quality of data is adequate to
  demonstrate no further action
• agreement on screening approach

81
Data CollectionTier 2 and Tier 3

• Objective is to demonstrate that concentrations
  of chemical(s) of concern at the point(s) of
  exposure will not be above acceptable levels or
  criteria
• for each exposure pathway identified
• Drivers
• site conceptual model
• concentrations of chemical(s) of concern
• fate and transport
• Technical policy decisions
• what quantity and quality of data is adequate to
  demonstrate no further action

82
Data Collection

• Representative of the site conceptual model AND

Chemical(s) of concern in the source area
Distribution of chemical(s) of concern
Variability in environmental conditions
Environmental media
Transport pathways
83
Tier Decisions
84
Risk-Based Corrective Action (RBCA) Process

• Encourages user-led initiatives
• Encourages stakeholder involvement
• Provides a framework for corrective action
• Recognizes the diversity of sites
• Encourages technical policy issues to be
  addressed up front
• Provides appendices for direction and examples

85
Tiered Decisions

• Decisions about chemicals of concern and pathways
  that are complete or potentially complete
• Decisions are made based on the tier evaluation

86
Tiered Decisions

• Complete or potentially complete pathways
• site conditions are above corrective action goals
• options interim remedial action, tier upgrade,
  remedial action
• site conditions are below corrective action goals
• option no further action
• Decisions are made as part of Tier 1, Tier 2 and
  Tier 3 Evaluations

87
RBCA Process Flow Chart
88
Decision Alternatives

• No further action
• pathway meets corrective action goal for the tier
• does not apply to chemicals or pathways for which
  there are no corrective action goals
• Interim action/risk reduction
• address immediate issues
• reduce migration or concentrations
• eliminate pathways and re-evaluate

89
Decision Alternatives

• Tier Upgrade
• complete or potentially complete pathways
• for pathways where no corrective action goals
  were developed or identified
• not available at Tier 3

90
Decision Alternatives

• Final remedial action
• develop remedial action performance criteria
  based on
• corrective action goals
• site conditions
• chemicals of concern
• pathways
• site use or redevelopment
• evaluate alternatives to meet goals

91
Decision Alternatives

• Choosing among the alternatives involves business
  decisions
• economic
• site use or redevelopment
• liability
• stakeholder issues
• All of the alternatives meet the same level of
  protectiveness

92
Why 3 Tiers (Levels) in RBCA?
Tier 1
More Site-Specific
Tier 2
More Conservative
Tier 3
Target Risk
Every tier achieves the same level of public
health protection
2
93
Tier Upgrade

• For chemicals and pathways where site conditions
  are above corrective action goals
• Compare with interim remedial action and final
  remedial action
• may be qualitative or quantitative
• Not available at Tier 3

94
What are the Drivers?

• Cost to implement each alternative
• Time and schedule concerns
• Stakeholder issues
• regulatory compliance factors
• acceptability to neighbors
• political issues
• Impacts of implementing each alternative
• e.g., short term impact to ecological habitats
  from active remedial action
• Site use or redevelopment
• transaction issues

95
Weighing the Alternatives
96
Weighing the Alternatives

• Start with common sense screening
• Is remedial action clearly the right choice given
  the site circumstances or would further tier
  evaluation be best?
• e.g., time sensitive redevelopment design system
  to meet current tiers corrective action goals
  rather than spending more time to develop higher
  tier corrective action goals
• If no clear choice then go to a more detailed
  analysis

97
Weighing the Alternatives

• Develop a common scale for evaluating the drivers
• common scale for assigning values to drivers for
  each alternative
• Where do each of the alternatives (i.e., tier
  upgrade, interim action, remedial action) fit
  based on each of the drivers?
• Compare qualitatively or semi-quantitatively
• Results of the comparison will be site specific
  based on the relative importance of the drivers
  at a particular facility

98
Example Qualitative Comparison

• Redevelopment site - shopping mall construction
  ready to begin now
• Option 1 Tier 2 remedial action
• extensive soil excavation, groundwater air
  sparging system
• Implement now
• Option 2 Tier Upgrade
• tier 3corrective action goals expected to result
  in limited soil excavation and engineering
  control system for groundwater
• 6 months for Tier Evaluation, then Implement

99
Example Qualitative Comparison Scale
100
Quantitative Analysis

• Formal decision analysis
• Develop decision trees including all of the
  alternatives
• Need to know
• the common value of implementing each alternative
• the consequences of success and failure
• the probability of success and failure

101
Quantitative Analysis

• Calculate the common value for each of the
  alternatives based on each of the drivers
• Compare the weighted average values (expected
  values) and choose the alternative with the
  highest expected value
• Common values can be expressed as monetary
  values, utilities, or another common scale

102
Example Comparison

• For one site the comparison between tier upgrade
  and remedial action looks like this

103
Example Comparison
0.7
104
Example Comparison
Expected Value probability of failurevalue of
failure probability of successvalue of
implementation
E(Tier Upgrade) (0.1)(-35)(0.9)(-25) -26
E(Remedial Action) (0.2)(-45)(0.8)(-20) -25
Choose Remedial Action
105
Remedial Options
106
Remedial Action

• Purpose of Remedial Action
• Definition
• The RBCA Paradigm
• Use of the site conceptual model
• Developing a holistic perspective
• Remedial action alternatives evaluation

107
Remedial Action

• Activities conducted reduce or eliminate current
  or potential future exposures to receptors or
  relevant ecological receptors and habitats
• These activities include
• monitoring
• implementing activity and use limitations
• designing and operating clean-up equipment
• other activities that are conducted to reduce
  sources of exposures to meet corrective action
  goals, or sever exposure pathways to meet
  corrective action goals

108
The Evolution of the Remedial Action Philosophy

• Pre RBCA
• What is the most we can clean up?
• Emphasis on mass reduction through technology
  for risk reduction

• Post RBCA
• What is clean up is necessary to be protective of
  human health and the environment?
• emphasis on technology and activity and use
  limitations for risk reduction

109
The RBCA Remedial Action Paradigm

• Is there a complete or potentially complete
  exposure pathway?
• How can we break the complete or potentially
  complete exposure pathway?
• reduce the source area
• eliminate the transport mechanism
• remove the receptor

110
Drivers for Remedial Action

• Concentrations of chemical(s) of concern are
  above the appropriate corrective action goals at
  the point of demonstration
• which COC are above the goals?
• RBSL, SSTL, RESC, SSEC
• what pathways are of concern?
• what media are affected?
• A higher tier evaluation is not warranted?

111
Remedial Action Performance Criteria

• Concentrations of chemical(s) of concern or ORMC
  in environmental media that are protective of
  human health and the environment for a given
  activity land use
• These goals may be based on
• generic (e.g., RBSL, RESC) or site-specific
  (e.g., SSTL, SSEC) corrective action goals
  developed during the Tier Evaluation
• regulatory standards (e.g, MCL)
• other performance criteria (e.g., aesthetic
  criteria)
• Criteria for establishing these goals should be
  acceptable to the regulatory agencies

112
The Holistic Approach to Selecting Remedial
Action Alternatives

• Remedial action has to achieve an adequate level
  of risk reduction for all COC phases for each
  complete or potentially complete exposure pathway
• Considerations necessary to achieve remedial
  action goals
• All exposure pathways
• Chemical(s) of concern
• Chemical properties (e.g., chemical, physical,
  toxicological)
• Subsurface characteristics
• Distribution of chemical(s) of concern in the
  environment
• Chemical phases

113
The Holistic Approach to Selecting Remedial
Action Alternatives

• Chemical properties and the characteristics of
  the environmental media define the phase and the
  distribution of chemical(s) of concern

114
The Holistic Approach to Selecting Remedial
Action Alternatives
115
The Holistic Approach to Selecting Remedial
Action Alternatives
116
Source Reduction
117
Source Reduction Technologies

• NAPL recovery
• Pump treat (dissolved phase)
• Natural attenuation
• High vacuum extraction
• Excavation

• Soil vapor extraction
• Bioventing
• Sparging
• Enhanced bioremediation
• Thermal technologies
• Chemical
• Oxidation

118
Source Reduction Considerations

• Source Type
• residual phase (soil sorbed)
• free phase (NAPL)
• vapor
• dissolved
• Mobility
• volatility
• solubility
• availability
• trapped residual phase
• Environmental media

• Chemical persistence
• Location
• surface soils
• subsurface soils
• unsaturated
• saturated
• NAPL on ground water surface
• NAPL below ground water surface
• sediments

119
Source Reduction Implications

• Does mass reduction result in significant risk
  reduction?
• Not Always
• with current technologies it may not be
  practicable to reduce residual NAPL in the
  saturated zone to a level that will result in
  acceptable dissolved concentrations
• recent studies predict that 80 - 90 of the
  saturated zone residual NAPL must be removed to
  affect the soluble plume

120
Source Reduction Implications

• Risk reduction in low permeability soil estimated
  to be negligible
• Risk reduction in high permeability soil can be
  good
• Field residual saturation controls the source
  reduction
• Low volatility chemicals are recalcitrant
• longer dissolution and attenuation times
• lower mobility plus higher residual saturation
• generally lower quantified risk
• Chemical alteration better when feasible

121
Source Reduction Implications

• Opinion
• many chemical(s) of concern plumes do not pose a
  risk
• leaving long-lived chemical(s) of concern plumes
  in place requires management mechanisms
• new technologies are needed

122
Source Reduction ImplicationsTechnology
Limitations

• Some methods limited in effectiveness
• ability of method to access the affected area
• Certain methods limited to amenable components
• e.g., volatile for SVE
• Phase-specific or component specific nature of
  some methods
• Prior success and experience for some methods
• Potential negative or adverse impacts of a method
• e.g., noise, dust

123
Source Reduction ImplicationsTechnology
Limitations

• Economics
• Time to complete
• Heterogeneity of soils
• Success hinges not on remedial action screening
  calculations but on understanding the
  hydro-geological characteristics and chemical
  distribution and relationship to clean up
  operation

124
Activity and Use Limitations in Remedial Action
125
Activity and Use Limitations

• Legal or physical restrictions or limitations on
  the use or access to a site or facility
• to eliminate or minimize potential exposures to
  COC
• to prevent activities that could interfere with
  the effectiveness of a remedial action
• to ensure maintenance of a condition of no
  significant risk to human health and the
  environment
• to prevent adverse impacts to individuals or
  populations that may be exposed to chemicals of
  concern
• focus on controlling human activity rather than
  containing or managing chemicals of concern

126
Activity and Use Limitations
127
Activity and Use Limitations
128
Activity and Use Limitations Types of Controls

• Proprietary controls
• State and local government controls
• Statutory enforcement tools
• Informational devices
• Engineering and access controls

129
Activity and Use LimitationsProprietary Controls

• Deed and Use Restrictions
• limits or conditions on the use and conveyance of
  land to
• inform prospective owner or tenant of existing
  condition
• ensure long-tern compliance and integrity of
  remedial action
• must satisfy several legal requirements
• written and recorded
• reflect mutual intention that restrictions run
  with the land
• compliance enforcement by third parties (privity
  of estate)
• address impacts that touch and concern land
• remedies for non-compliance includes seeking an
  injunction or civil penalties (e.g., fines)

130
Activity and Use LimitationsProprietary Controls

• Restrictive covenant
• provisions in a deed limiting the use of the
  property and prohibiting certain uses
• in context of property law the term describes
  contract between grantor and grantee for
  grantee's use and occupancy of land
• general purpose is to maintain or enhance value
  of lands adjacent to one another by controlling
  nature and use of surrounding lands
• not a permanent part of the property record or
  property title for flexibility to re-convey the
  property

131
Activity and Use LimitationsProprietary Controls

• Easements
• a right of use over the property of another
• traditionally limited uses
• rights of way and rights concerning flowing
  waters
• normally for the benefit of adjoining lands, no
  matter who the owner is rather than for the
  benefit of a specific individual
• may allow access to the property or prohibit a
  use of the property
• grant state authorities or others an easement for
  operation and maintenance of engineering controls
  or for general inspection/audit functions

132
Activity and Use LimitationsState and Local
Government Controls

• Restrictive zoning
• imposed by municipal or local government
  authorities
• prohibit residential uses in a formerly
  industrial area
• can not limit uses or activities at individual
  sites
• Local jurisdiction review of activity and land
  use controls before issuing building permits
• Water and well use advisories
• alert the public to potential risks from ground
  water
• recorded in the land record
• presented in the form of public notice of
  remedial action as part of the federal or state
  program

133
Activity and Use LimitationsState and Local
Government Controls

• Well restrictions that prohibit or condition the
  construction of ground water wells in an area
• permitting
• prohibit construction of a private well without
  permit
• limited water quality testing and well
  inspections prior to use
• overlay zoning
• zones drawn on zoning map to provide protection
  not explicitly stated under existing zoning
  regulations
• aquifers and quality designation through
  classification system
• local and county ordinances
• restrict the use of ground water in cases where
  the existing water supply on a property is a
  potential threat to health

134
Activity and Use LimitationsStatutory
Enforcement Tools

• Regulatory agency may have enforcement
  authorities that can be used to impose activity
  and use limitations
• administrative orders or a court order whenever
  there is an imminent and substantial endangerment
  to public health, welfare or the environment
• only binding on responsible party not subsequent
  owners
• a facility operating permit (e.g., under RCRA) or
  corrective action permit may be a vehicle for
  imposing activity and use limitations
• binds only the permittee for life of permit

135
Activity and Use LimitationsInformation Devices

• Notices
• tool to ensure that parties to a real estate
  transaction are aware of the environmental status
  of the property prior to finalizing a
  transaction.
• may be informational only
• may be an integral enforceable part of activity
  use controls
• usually requires disclosure of the specific
  environmental condition of a site and any
  restrictions on use, access and development of
  part or all of the property
• record notice
• actual notice to the other party to a real estate
  transaction
• notice to the appropriate government authority

136
Activity and Use LimitationsInformation Devices

• Registry requirements
• a list maintained by a regulatory or other
  government agency of all properties that have
  been the site of hazardous waste disposal and
  that have restrictions on use or transfer
• Transfer requirements
• specific regulatory program that require full
  evaluation of the environmental condition of a
  site before or after a transfer occurs
• typically creates information disclosure
  obligations on the seller or lessor of property

137
Activity and Use LimitationsEngineering Controls

• Technology based, physical modifications to a
  site or facility to reduce or eliminate potential
  for exposure to a chemical(s) of concern
• Hydraulic containment
• physical barrier
• slurry walls
• fences
• capping
• point of use water treatment
• positive pressure (prevent vapor intrusion)

138
Activity and Use LimitationsEngineering Controls

• Considerations
• location
• residential or mixed use neighborhood
• surroundings
• near sensitive land use areas, such as day care
  centers, playgrounds, schools
• usage
• frequently used or traversed by area residents or
  local workers
• maintenance and monitoring
• duration of the potential exposure

139
Activity and Use LimitationsBarriers to Use

• Real estate preference and misunderstanding
• concern for property cost devaluation
• stigma
• controls that prevent or control use should not
  contribute to significant property devaluation
• reliability of the controls
• Inadequate regulatory authority or programs
• enforcement to ensure controls remain in place
• Legacy of past problems
• liability and financial responsibility

140
Factors for Consideration in Remedial Action
Selection
141
Key Questions for Remedial Action

• Is the situation stable?
• is there limited or no migration potential of
  chemical(s) of concern?
• Is there a need to implement remedial action
  immediately to address a significant potential
  exposure?
• Will active source reduction reduce overall risk
  (all phases considered) to an acceptable level?
• if active remedial action is not likely to reduce
  overall risk in a reasonable time, should this
  still be considered?

142
Key Questions for Remedial Action

• Is containment an appropriate alternative?
• will containment protect receptors?
• will source reduction reduce the containment
  lifetime?
• is the source reduction technology likely to be
  successful and cost-effective versus containment?
• Are activity and use limitations appropriate with
  or without remedial action?
• Are there potential redevelopment or future land
  use issues that need to be considered?

143
Key Questions for Remedial Action

• What remedial action alternative or combination
  of alternatives can achieve the corrective action
  goals for the complete or potentially complete
  exposure pathways at the point(s) of
  demonstration?
• source reduction
• engineering controls
• activity and use limitations for contributing
  chemical phases

144
Factors for Consideration in Remedial Action
Selection

• Effectiveness
• Reliability
• Short-term risk
• Integration with property use
• acceptability
• Implementability
• Ecological
• Cost effectiveness

145
Remedial Action SelectionEffectiveness

• Ability of remedial action alternative to achieve
  the corrective action goals
• In some cases it may be technically impracticable
  to achieve the appropriate remedial action goals
• activity and use limitations should be considered
• Regional factors may also influence overall
  effectiveness
• background concentrations of COC
• location of other potential sources

146
Remedial Action SelectionReliability

• The potential of the remedial action to achieve
  and maintain the corrective action goals
• New technologies are continually being developed
• may not have an established performance history
• both their short-term and long-term reliability
  are subject to question

147
Remedial Action SelectionShort-Term Risk

• Short-term risk posed by the implementation of
  the remedial action to
• the affected community
• those engaged in the remedial action effort
• relevant ecological receptors and habitats
• example excavation may involve
• aesthetic impacts to the local community
• heath and safety risks to excavation contractors
• increased potential for a transportation accident
• damage or destruction of ecological receptors or
  habitats
• future risk and liabilities at disposal site

148
Remedial Action SelectionIntegration with
Property Use

• Consideration of potential redevelopment and
  current use of the property in selection, design
  and implementation of remedial action alternative
  
• Redevelopment of the site
• short term objectives
• long term objectives
• delayed or accelerated implementation
• location of equipment

149
Remedial Action SelectionAcceptability

• Consideration of the acceptability of the
  remedial action to the affected community and
  other potential stakeholders
• it is important to keep stakeholders involved in
  the process to provide awareness of the issues
  and prevent potential conflicts at the end of the
  project
• buyer or lender requirements in a property sale
• regulatory compliance and acceptability of the
  selected remedial action alternative
• available regulatory oversight or voluntary
  action program
• insurer or management requirements related to
  future liabilities

150
Remedial Action SelectionImplementability

• Consideration of the technical and physical
  issues that will affect the implementation of the
  remedial action considering site constraints
• geological factors
• soil heterogeneity and discontinuities
• surface factors
• location constraints due to existing physical
  structures
• political or regulatory constraints
• ability to obtain permits
• logistics of scale-up of new technology

151
Remedial Action SelectionEcological

• Remedy selection always involves tradeoffs
• Need to balance the consequences of actions taken
• Can occur when considering human health and the
  environment
• Example
• implementation of remedial action to protect
  human health will destroy ecological health in
  the areas where remedial action will occur
• What options can be selected to protect human
  health while leaving the environment intact?

152
Remedial Action SelectionCost Effectiveness

• Reasonableness of cost
• selection of the most cost effective alternative
• including activity and use limitations where
  source reduction is unreasonable
• consideration of
• cash flow
• net present value
• development of new technologies
• impact on property values
• total cost or life cycle costs
• available funding to complete the project

153
Additional Factors Influencing the Type of
Remedial Action Selected

• Regulatory compliance / acceptability (e.g., RNA)
• Buyer or lender requirements in a property sale
• Re-use / redevelopment of site
• short term objectives
• long term objectives
• Good neighbor issues

154
Additional Factors Influencing the Type of
Remedial Action Selected

• Insurer or management requirements related to
  future liabilities
• Total cost or life cycle costs
• Available regulatory oversight or voluntary
  clean-up program

155
Remedial Action Cost Categories

• Capital Costs
• direct costs
• construction
• site development
• buildings and services
• demolition and decommissioning
• indirect costs
• engineering design (before/during construction)
• supervision
• permitting and legal
• other

• Operation and maintenance costs
• labor
• supervision
• health and safety
• chemicals
• equipment
• materials
• utilities
• insurance and taxes