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Dr. Mengfang Chen, Royal Haskoning, UKRic Bowers, GSI Environmental, USA
RBCA Tool Kit V2 a real alternative to CLEA model
Brownfield Briefing Contaminated Land Risk Assessment 2008 29th April 2008
Brief History of RBCA and CLEA
RBCA Tool Kit V2
Key Compatibility Issues Examined
SGV Validation Testing
Summary
Outline of the Presentation
CLR10 Update with Briefing Notes
2005
DEFRA
Way Forward
DEFRA and EA: CLR11
DEFRA and EA:
CLR10, SGV, TOX Reports
DETR
No Risk Based Guidance
(ICRCL, Dutch, ASTM RBCA)
UK
No Further Guidance
ASTM E2081
ASTM P104
Chemical RBCA
ASTM E1839
Petroleum RBCA
USEPA RAGS
USA
2006200420022000199819951989Guidance
?????CLAN6/06CLEA-UKCLEA2002CLEA2000CLEA97Start of CLEA
2008
Public Debating and Continuing
Model Development
CLEA
200620052002200019971992Model
RBCA V2RBCA Tool Kit V1.3RBCA Tool Kit V1.0
Tier 2 RBCA Tool Kit
2008
Model Improvement and UK ComplianceModel Development
RBCA
200019991996Model
Brief History of CLEA and RBCA
Monte Carlo versus Deterministic
Plant Uptake
Vapours from Surface Soil
CLEA-UK Versus RBCA Toolkit V1.3
(2005)
Monte Carlo versus Deterministic
Plant Uptake
Dermal Contact
Indoor and Outdoor Vapours
CLEA2002 Versus RBCA Toolkit V1.3
(2002)
Almost Identical Except RBCA having:■ More algorithms available to choose on
vapour pathways such as mass balance and USEPA SSG Q/C model for outdoor
■ Groundwater Vapour Onsite and Offsite■ Controlled Water or Water Environment
Risk Assessment■ Soil and Groundwater Source Depletion for
DQRA
FUTURE CLEA Based on CLAN6/06 Versus RBCA Toolkit V2
(2008 and beyond)
Differences in Model Functionalities
Brief History of CLEA and RBCA
Identical (USEPA Dermal Absorption Method)6) Dermal Contact
Identical (ASTM Johnson & Ettinger)3) Indoor Vapour2
Identical (USEPA Q/C Model)5) Particulates/Dusts
Identical (ASTM Subsurface Equation)4) Outdoor Vapours2,3
Identical (Briggs Routine for Organics and Direct Input for Metals, but Adjustments
Required for Certain Parameters)
2) Consumption of Home grown vegetable1
ASTM/USEPA1) Soil and Dust Ingestion
CLEA UKRBCA V2Exposure Pathway
Note: 1) RBCA does not have a pathway for indirect soil ingestion attached to vegetable
2) RBCA also has ASTM mass balance checks for vapour pathways
3) RBCA also has additional algorithms: ASTM surface soil and USEPA Q/C model for outdoor vapour pathway
Technical Algorithms – Human Health
Brief History of CLEA and RBCA
INCREASING NEED FOR SITE SPECIFIC DATA AND REDUCED CLEAN-UP COST
Soil: SGV CLEA UKGW: RTM, ConSim
Soil: CLEA UKGW: RTM, ConSim
MODFLOW, RT3DMT3DMS, ADMSAEROMOD
Hazard Identification
Magnitude of Consequences
Probabilities of Consequences
Identification ofConsequences
Risk B
ased R
emed
ial So
lutio
ns
TIER 4(DQRA)
Assessment of Controlled Water Risks (SSAC)
TIER 2(GQRA)
Assessment Under Generic Conditions – GAC
RBCA Tier 1
RTM Tier 1 & Tier 2
TIER 1
CSM Risk Screening
Qualitative RA
Significance of Risk
Brief History of CLEA and RBCA
Risk Based, Tiered Framework
Typical Model Used
Quantitative Risk Assessment
INCREASING COMPLEXITY & LEVEL OF EFFORT
TIER 3(DQRA)
Assessment Under SiteSpecific Condition - SSAC
RBCA Tier 2/3
RTM Tier 3 &Tier 4
RBCA Tool Kit Features
User-Input Target Risks
Chem/Tox Database
Standard Exposure Factors
Analytical Fate & Transport Models
x =x
RBCA Tool Kit V2 includes system of analytical models for comprehensive evaluation of air, soil, and groundwater exposure pathways
RBCA Tool Kit V2
Main Screen
Soil and Groundwater Source Depletion Algorithms for DQRA
Tiered Structures Tier 1 and Tier 2/3 Equivalent to CLR 11 Tier 2 (GQRA) and Tier 3 (DQRA)
RBCA Tool Kit V2
Chemical / Toxicological Database
600 Chemicals: Petroleum Hydrocarbons/TPH
SVOC/PAHs
Chlorinated Solvents
Pesticides
Metals
RBCA Tool Kit V2
■ Adding or Editing Chemical Data■ Save as project specific database for QA purpose■ Reserved columns for UK CLEA Tox data■ Selection of preference of tox data from USA, Dutch and UK
Exposure Pathway Input
Applicable Pathways
Multiple Receptors
Mixed Land Uses
■ Groundwater Ingestion■ Surface recreational and fish consumption■ Soil ingestion, dermal contact, inhalation of vapors and
particulates, and consumption of homegrown vegetables)■ Outdoor and indoor inhalation of vapors emanating from soil
or groundwater sources
RBCA Tool Kit V2
Exposure Factors
Exposure Rates
Risk Limits (Target Hazard Quotient/Index, and Target Cancer Risk Limits)
Defining Open Space/Parks Land Use
RBCA Tool Kit V2
Fate and Transport Models
Cross-Media Transfer with multiple fate and transport models to select from
Lateral Air and Groundwater Transport (Off-site)
RBCA Tool Kit V2
Site-Specific Inputs
Cross-Media Transfer with multiple fate and transport models to select from
Lateral Air and Groundwater Transport (Off-site)
RBCA Tool Kit V2
Output
Pathway and Depth Specific GAC/SSAC
Summary of Chemical Parameters
Detailed Exposure and NAF Calculations
Summary of Exposure, Building, Air, Soil and Groundwater Parameters
RBCA Tool Kit V2
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√
√
√
√
√
√
√
Residential with
Plant Uptake
√Consumption of Site Grown Vegetable
√Indirect Soil Ingestion Attached to Vegetable
√√√Inhalation of Soil Derived Outdoor Dust
√√√Inhalation of Soil Derived Indoor Dust
√√√Dermal Contact with Soil (Outdoor)
√√√Dermal Contact with Soil Derived Indoor Dust
√
√
√
Allotment
√√Inhalation of Soil vapour - Outdoor
√√Inhalation of Soil Vapour – Indoor
√√Direct Soil Derived Indoor Dust Generation
√√Direct Soil Ingestion
Commercial
Residential without
Plant Uptake
Exposure Pathways
Modifications/Adjustment
Note: 1) Exposure pathways highlighted are not included in RBCA, but can be implemented by manipulating interfaces and input parameters
Standard Land Uses and Exposure Pathways
Modifications/Adjustment
Incorporating CLR10-Specific Data: Human, Exposure, Air, Building and Soil Parameters
Converting Henry Law Constant to 10° C (Soil Temperature)
TDSI as Input (Not TDI) to Consider Background Exposure
Considering Soil Enrichment Factor and Fraction of Locally Derived Soil in Building Dust for Inhalation of Particulates
Using UK-Specific Respiratory Volumes to Adjust Exposure Frequencies for Inhalation of Indoor and Outdoor Vapours/Dusts
Manipulating Interfaces and Input parameters to include Three Missing Exposure Pathways
Integration of Pathway-Specific GAC/SSAC
Key Modifications/Adjustments Required
Modifications/Adjustment
CLEA-UK: Briefing Note 4Harmonic Mean
RBCA Tool Kit: ASTM E2081Combined Harmonic Mean and Minimum Approach
∑=
=n
n nGAC
GAC
1
11
Where n = number of exposure pathways depending on land uses
∑=
= n
n n
SS
GAC
GAC
1
11
Where GACSS representing GAC for Surface Soil Exposures, and n = number of surface soil exposure pathways (i.e oral, dermal, vegetable consumptions, particulates and outdoor vapour from surface soil) depending on land uses
),,min( __ VOutdoorVindoorSS GACGACGACGAC =
Integration of Pathway Specific GAC/SSAC
Modifications/Adjustments Required
Residential and Allotment Land Uses Exploring Impact of CLAN6/06 on the Published SGV (i.e Soil
Ingestion Rate = 100 mg/d) Manipulating Soil Ingestion Rate and Bodyweight in order to
reproduce SGV (key parameters with PDF functions) for Metals
Use 5th percentile BW (11.15kg) and calibrate on Soil Ingestion Rate
Commercial/Industrial Land Use Fixed Soil Ingestion Rate (40 mg/d) Specifying 5th percentile Body Weight (46.4 kg) to reproduce
SGV for Metals
Modifications/Adjustment
Soil and Dust Ingestion
Modifications/Adjustments Required
Calculating UK-Specific Exposed Skin Surface Areas for Children and Adult Based on CLEA Briefing Note 1
Setting Up Two Models: Dermal Indoor and Outdoor
Incorporating FDUST for Dermal Indoor Model
Modifications/Adjustment
Dermal Contact: Indoor and Outdoor
Modifications/Adjustment
Modifications/Adjustments Required
General Calculating UK-Specific Time Averaged Respiratory Volumes
Based on CLR10 Adjusting Exposure Frequencies incorporating UK-specific
respiratory volume and body weight Or manipulating RfC incorporating UK-specific respiratory
volumes and body weightIndoor Vapour Use of default sandy soils with SOM (1, 2.5 and 5%) and
building parameters to reproduce SGV for ethylbenzene and toluene
Outdoor Vapour Use of UK Specific Air Parameters
Inhalation of Indoor and Outdoor Vapours
Modifications/Adjustment
Modifications/Adjustments Required
General Calculating UK-Specific Time Averaged Respiratory
Volumes Based on CLR10 Adjusting Exposure Frequencies incorporating UK-specific
respiratory volume and body weight Or manipulating RfC incorporating UK-specific respiratory
volumes and body weightIndoor Particulates Incorporating Soil Enrichment Factor and FDUST for metals
and BaP; FDUST for other contaminants
Outdoor Particulates Incorporating Soil Enrichment Factor for metals and BaP
Inhalation of Particulates: Indoor and Outdoor
Modifications/Adjustment
++=
asococwssw
HfKK
θρθρ
,,
ssw ss
T s oc oc ssK
K f
ρθ ρ
=+
Adjustments Required
Time averaged or 5th percentile BW Derive Consumption Rates for Leafy and Root
Vegetables Application of DW Conversion Factors to CF
for metals Application of Ksw (Soil to Leachate
Coefficients) Correction Factor
CLEA UK
RBCA V2
Adjustments Required
Time averaged or 5th percentile BW Derive Equivalent Soil Ingestion Rates for
Leafy and Root Vegetables Use Soil Ingestion Interface for Exposure
Calculations
Consumption of Home-Grown Vegetable
Indirect Ingestion of Soils Attached to Vegetable
CLEA Briefing Note 4Integration
NA
Ingestion of Soil Attached to Vegetable:
Leafy: 4.6 mg/d
Root: 3.7 mg/d
Ingestion of Garden Vegetable:
Leafy: 4640 mg/d
Root: 13800 mg/d
Vegetable Consumption Rates
Time Averaged
Indoor: 4.73 m3/d
Outdoor: 0.95 m3/d
Time Averaged
Indoor: 3.98 m3/d
Outdoor: 1.06 m3/d
Respiration Volumes
5th percentile: 46.4 kg5th percentile: 11.15 kgBody Weight
OfficeTwo Storey HouseBuilding
Sandy Soil
SOM – 1%, 2.5% and 5%Soil Properties
Indoor: 56 days/y
Outdoor: 8 days/y
Indoor: 351 days/y
Outdoor: 93 days/yExposure Frequencies for Vapour and Dust
SGV Contaminants
155 mg/d
Residential
40 mg/dSoil and Dust Ingestion Rate
Contaminants Evaluated
CommercialParametersAssumptions for Validation
SGV Validation Testing
Anticipated Outcome
SGV Validation Testing
Identical SGV for vapour or oral pathway driven contaminants
Variations expected for plant uptake where significant (Time averaged approach for vegetable consumption rates)
SGV Reproduced for Commercial and Residential without Plant Uptake
SGV Reproduced for Residential with Plant Uptake except for Cadmium and Selenium
788039411616Ethylbenzene
15158833Toluene
RBCACLEARBCACLEARBCACLEA
5% SOM2.5% SOM1% SOM
Soil Guideline Values (mg/kg)
COC
481564800048156480004815648000Ethylbenzene1
677680347350148150Toluene
RBCACLEARBCACLEARBCACLEA
5% SOM2.5% SOM1% SOM
Soil Guideline Values (mg/kg)COC
4441222199Ethylbenzene
14147733Toluene
RBCACLEARBCACLEARBCACLEA
5% SOM2.5% SOM1% SOM
Soil Guideline Values (mg/kg)
COC
SGV Validation Testing
Residential Without Plant Uptake
Residential With Plant Uptake
Commercial/Industrial
Note: 1) SGV for ethylbenzene has been derived by setting target hazard quotient = 0.36 for soil ingestion and dermal pathways due to saturated vapour concentrations predicted
51545000131130190200Chromium
82
51
7
2.8
18
RBCA
35
50
8
2
20
CLEA SGV
Residential With
Plant Uptake
RBCACLEA SGVRBCACLEA SGV
79168000259260Selenium2
497050007275Nickel
4794801615Mercury
141714003430Cadmium1,2
5525002120Arsenic
CommercialResidential Without Plant Uptake
CoC
SGV Validation Testing
Note: 1) only pH = 7 is evaluated and 2) Variations caused by large contributions to the total exposure representing 95% and 80% respectively for cadmium and selenium
RBCA and CLEA Having Identical Technical Algorithms
RBCA and CLEA Even More Closer Following CLAN6/06 Recommendations
Modifications/Adjustments Required to Comply with CLEA-UK Model (& RTM Soil and Groundwater)
Validation Testing Indicating Near-Perfect Match
RBCA Offering A Real Alternative to Future CLEA
Summary