introduction to atlantic rbca version 3

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



>C16-C21



>C21-C32



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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• 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)


Xylenes 10 Tier II SSTL (GW ing)

Modified TPH 240 Tier II SSTL (IA)


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)


Xylenes 6.4 Tier II SSTL (GW ing)

Modified TPH 500 Tier II SSTL (IA)


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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introduction to atlantic rbca version 3

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