Introduction to Atlantic RBCA Version 3
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Introduction to Atlantic RBCA Version 3
Webinar May 4, 2013
Attending Today’s Session
• Hosting– Tania Noble, Stantec– Michel Poirier, NBENV– Ulysses Klee, Stantec
• You – People who have taken the on-line course
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Outline• Quick Navigation (Webinar)• Questions asked during
course or submitted for the webinar
• Reminder of topics/other questions on theory
• Review Case Studies from course
Q1 – Incorporating lab results
Tier I Tier II Tool kit – version 3
Benzene Benzene Benzene
Toluene Toluene Toluene
Ethylbenzene Ethylbenzene Ethylbenzene
Xylenes Xylenes Xylenes
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Q1 – Incorporating lab results
Tier I Tier II Tool kit – version 3
C6-C10 hydrocarbons Aliphatic C6-C8 Aliphatic >C6-C8
Aliphatic >C8-C10 Aliphatic >C8-C10
Aromatic >C8-C10 Aromatic >C8-C10
>C10-C16
hydrocarbonsAliphatic >C10-C12 Aliphatic >C10-C12
Aliphatic >C12-C16 Aliphatic >C12-C16
Aromatic >C10-C12 Aromatic >C10-C12
Aromatic >C12-C16 Aromatic >C12-C16
>C16-C21
hydrocarbonsAliphatic >C16-C21 Aliphatic >C16-C21
Aromatic >C16-C21 Aromatic >C16-C21
>C21-C32
hydrocarbonsAliphatic >C21-C32 Aliphatic >C21-C34
Aromatic >C21-C32 Aromatic >C21-C35
Modified TPH – Tier I
Modified TPH – Tier II
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Return to Baseline at C32? (yes/no)?
Return to Baseline at C32? (yes/no)?
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Q2 –Modeling different pathways
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Q2 –Modeling different pathways
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Q2 –Modeling different pathways
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Q2 –Modeling different pathways
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Q2 –Modeling different pathways
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• Best Practice:– Run each pathway separately
• Indoor Air (x 10)• Dermal Contact and Soil Ingestion• Groundwater Ingestion
– Run TEX separately from TPH
Might seem like a lot of runs for some sites, but it will greatly reduce the chance of error
Q3 – Minimum Requirements for AF=10?
• Same as basic requirements for using model– Concrete floor– 30 cm clean soil separation
• Can still adjust other building parameters as usual and apply AF=10 for BTEX/TPH
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Q4 – How can you adjust crack fraction?
• Crack fraction = Acracks/Abldg
• Default crack fraction assumes:– Perimeter crack only– From CWS: crack width = 0.2 cm
for residential, = 0.26 cm for commercial
• For all other openings, note dimensions, calculate area, and add to perimeter crack
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Q5 – Adjust for dirt floor (internal purposes only)
• Technically: Adjust the crack fraction to 1.0
• Note: Once you go beyond the range of “typical” values (0.0001 to 0.01), model may become unstable, and results may become very sensitive to other parameters
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Q6 – Relevant Parameters for Indoor Air Pathway
• Does depth to contamination matter?– Depends. If diffusion through
soil to foundation is dominant process, yes
– If advection dominates, then SSTL is not sensitive to depth to contamination
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Q6 – Relevant Parameters for Indoor Air Pathway
• Does area of contamination matter?– Area of impact on soil input
parameters does not affect SSTL for indoor air pathway
– Account for soil area through volume to area ratio
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Q7 – Equation for estimating dispersivity
• Xu and Eckstien equation is recommended over ASTM
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Q8 – What if you don’t know the wind direction?
• For air dispersion model, if you don’t know wind direction, assume receptor is directly downwind
• Similar recommendation for groundwater dispersion if you are uncertain about groundwater direction
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Reminder of the Topics• M1 – Introduction• M2 – Overview• M3 – RA Fundamentals• M4 – Evaluating Exposure Pathways• M5 – Fate and Transport• M6 – ARBCA Model Issues• M7 – Model Sensitivity• M8 – Navigating the ARBCA Toolkit• M9 – Version 2 User Guidance• M10 – Soil Vapour & IA Monitors• M11 – Atlantic Regulatory Process• M12 – Final Test
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Case Study #1
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Case Study #1
• Provided only 1 soil sample and 2 MW samples & table of site-specific conditions
• Assumptions:– Full site characterization has
been completed– Building has no major
openings in concrete floor and is at least 2 levels
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Case Study #1Soil Remedial Criteria (mg/kg)
Benzene 0.042 Max < Tier I RBSL
Toluene 0.35 Max < Tier I RBSL
Ethylbenzene 0.061 Tier II SSTL (GW ing)
Xylenes 10 Tier II SSTL (GW ing)
Modified TPH 1200 Max > Tier II SSTL (IA)
Groundwater Remedial Criteria (mg/L)
Benzene 0.005 Max < Tier I RBSL
Toluene 0.024 * GCDWQ (Max > criteria)
Ethylbenzene 0.0024 Max < Tier I RBSL
Xylenes 0.3 Max < Tier I RBSL
Modified TPH 5.9 Max > Tier II SSTL (GW ing)
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Case Study #2
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Case Study #2• Provided limited sample results;
no info on surrounding land use• Assumptions:
– Full site characterization has been completed
– Building has no major openings in concrete floor
– Surrounding land use is commercial– Mixed use on-site – residential most
conservative
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Case Study #2 – Gas/DieselSoil Remedial Criteria (mg/kg)
Benzene 0.042 Max (nd) < Tier I RBSL
Toluene 0.33 Tier II SSTL (GW ing)
Ethylbenzene 0.061 Tier II SSTL (GW ing)
Xylenes 10 Tier II SSTL (GW ing)
Modified TPH 240 Tier II SSTL (IA)
Groundwater Remedial Criteria (mg/L)
Benzene 0.005 * GCDWQ
Toluene 0.024 * GCDWQ
Ethylbenzene 0.0024 * GCDWQ
Xylenes 0.3 * GCDWQ
Modified TPH 17 Tier II SSTL (GW ing)24
Case Study #2 – Weathered DieselSoil Remedial Criteria (mg/kg)
Benzene 0.042 Max (nd) < Tier I RBSL
Toluene 0.22 Tier II SSTL (GW ing)
Ethylbenzene 0.038 Tier II SSTL (GW ing)
Xylenes 6.4 Tier II SSTL (GW ing)
Modified TPH 500 Tier II SSTL (IA)
Groundwater Remedial Criteria (mg/L)
Benzene 0.005 * GCDWQ
Toluene 0.024 * GCDWQ
Ethylbenzene 0.0024 * GCDWQ
Xylenes 0.3 * GCDWQ
Modified TPH 4.9 Tier II SSTL (GW ing)25
Case Study #3 26
Case Study #3• Original report and
assessment dates back prior to 2003– Did you pick up on changes
between how report was RBCA was used then, versus how you did it now?
– How did you address:• Vapour screening?• Bedrock• Off-site wells? 27
Case Study #3
• What assumptions did you have to make?
• What other information would you have liked to have?
• Based on your assessment, does this site require further mediation or risk management?
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Suggestions or comments
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