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 2

3 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 ITier IITool kit – version 3 Benzene Toluene Ethylbenzene Xylenes 4

Q1 – Incorporating lab results Tier ITier IITool kit – version 3 C 6 -C 10 hydrocarbonsAliphatic C 6 -C 8 Aliphatic >C 6 -C 8 Aliphatic >C 8 -C 10 Aromatic >C 8 -C 10 >C 10 -C 16 hydrocarbonsAliphatic >C 10 -C 12 Aliphatic >C 12 -C 16 Aromatic >C 10 -C 12 Aromatic >C 12 -C 16 >C 16 -C 21 hydrocarbonsAliphatic >C 16 -C 21 Aromatic >C 16 -C 21 >C 21 -C 32 hydrocarbonsAliphatic >C 21 -C 32 Aliphatic >C 21 -C 34 Aromatic >C 21 -C 32 Aromatic >C 21 -C 35 Modified TPH – Tier IModified TPH – Tier II- Return to Baseline at C 32 ? (yes/no)? - 5

Q2 –Modeling different pathways Run inhalation pathways separately from ingestion pathways >C16 hydrocarbons non-volatile (no inhalation toxicity information) but do contribute to oral exposures If you try to run both pathways together, the contributions of the non-volatile hydrocarbons to oral exposures will not be assessed 6

Q2 –Modeling different pathways Model: Well Dilution Factor (WDF) versus Lateral Dilution Attenuation Factor (DAF) WDF – typical area of impact is not sufficient to supply even a 2 person family. WDF accounts for how much “clean” water will be mixed with impacted water to meet demand DAF – as a plume moves away from the source area, the concentrations decrease. DAF estimates what the downgradient concentration will be 7

Q2 –Modeling different pathways Run TEX separately from TPH The target hazard quotient (THQ) for TEX is 0.5, but THQ for TPH is 1.0 Tool kit only has one location to input THQ 8

Q2 –Modeling different pathways Run Indoor Air Pathways Separately from all other Pathways for TPH The adjustment factor (AF) of 10 must be applied to the SSTL at the end The tool kit selects the lowest SSTL for each sub- fraction for calculator – possibility of mixing SSTLs that need AF of 10 with those that don’t 9

Q2 –Modeling different pathways 10 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 11

Q4 – How can you adjust crack fraction? Crack fraction = A cracks /A bldg 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 12

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 ( to 0.01), model may become unstable, and results may become very sensitive to other parameters 13

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 14

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 15

Q7 – Equation for estimating dispersivity Xu and Eckstien equation is recommended over ASTM 16

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 17

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 18

Case Study #1 19

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 20

Case Study #1 Soil Remedial Criteria (mg/kg) Benzene0.042Max < Tier I RBSL Toluene0.35Max < Tier I RBSL Ethylbenzene0.061Tier II SSTL (GW ing) Xylenes10Tier II SSTL (GW ing) Modified TPH1200Max > Tier II SSTL (IA) Groundwater Remedial Criteria (mg/L) Benzene0.005Max < Tier I RBSL Toluene0.024* GCDWQ (Max > criteria) Ethylbenzene0.0024Max < Tier I RBSL Xylenes0.3Max < Tier I RBSL Modified TPH5.9Max > Tier II SSTL (GW ing) 21

Case Study #2 22

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 23

Case Study #2 – Gas/Diesel Soil Remedial Criteria (mg/kg) Benzene0.042Max (nd) < Tier I RBSL Toluene0.33Tier II SSTL (GW ing) Ethylbenzene0.061Tier II SSTL (GW ing) Xylenes10Tier II SSTL (GW ing) Modified TPH240Tier II SSTL (IA) Groundwater Remedial Criteria (mg/L) Benzene0.005* GCDWQ Toluene0.024* GCDWQ Ethylbenzene0.0024* GCDWQ Xylenes0.3* GCDWQ Modified TPH17Tier II SSTL (GW ing) 24

Case Study #2 – Weathered Diesel Soil Remedial Criteria (mg/kg) Benzene0.042Max (nd) < Tier I RBSL Toluene0.22Tier II SSTL (GW ing) Ethylbenzene0.038Tier II SSTL (GW ing) Xylenes6.4Tier II SSTL (GW ing) Modified TPH500Tier II SSTL (IA) Groundwater Remedial Criteria (mg/L) Benzene0.005* GCDWQ Toluene0.024* GCDWQ Ethylbenzene0.0024* GCDWQ Xylenes0.3* GCDWQ Modified TPH4.9Tier 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? 28

Suggestions or comments 29