Temperature and Vapor Intrusion Evaluation Evelina Morales, Ph.D. Oklahoma DEQ, Land Protection Division 405 702-5108 Evelina.morales@deq.state.ok.us Presented at: 18 th Annual AEHS Meeting and West Coast Conference on Soils, Sediments, and Water March 12, 2008, San Diego, CA
Disclaimer The views expressed in this presentation are those of the author and do not reflect policy or endorsement of the Oklahoma Department of Environmental Quality.
Oklahoma s VI Evaluation Policy: Similar to the protocols followed by other states. Guided by the ITRC 2007 Vapor Intrusion Pathway: A Practical Guideline EPA 2002 Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance)
Phases of Oklahoma s VI Policy 1. Determination if vapor intrusion pathway is complete. 2. Determination if site characterization is adequate. Sampling of groundwater, soil gas, background Subsurface soil investigation
Phases of.. 3. Evaluation of data - compare to target levels - use of J&E model, if planned - use multiple lines of evidence 4. Remediation or Mitigation
This presentation is about the use of J&E modeling in the evaluation of data, specifically on the effect of default and site specific soil and groundwater temperatures on incremental risk.
EPA Fact Sheet, June 2001, Correcting the Henry s Law Constant for Soil Temperature, states that: Average subsurface soil temperature is typically less than 25 o C (page 1 of Fact Sheet).
But our data for evaluation: are not average data. Soil temperatures are not taken or recorded. Groundwater temperatures are not taken. (they were not asked for in the Guidance) The range of groundwater temperature 57 o - 67 o F (14 o -19.5 o C) for Oklahoma adds to the dilemma on what temperature to use.
So, we decided to: Be site specific!
To test if that is the right decision, we run the J&E model for the incremental risk on 2 sites: Site A: Miami, OK Site B: Midwest City, OK
Soil and groundwater temperatures were estimated from a software using the ambient temperature at the time of sample collection.
http://soilphysics.okstate.edu/software/index.html Soil Temperature Changes With Time and Depth, version 2005 Soil temperature fluctuates annually and daily affected mainly by variations in air temperature and solar radiation. The annual variation of daily average soil temperature at different depths can be estimated using a sinusoidal function (Hillel, 1982; Marshall and Holmes, 1988; Wu and Nofziger, 1999). This program estimates daily soil temperatures and displays these values as functions of time or depth for user defined input parameters.
SITE A MIAMI, OK COC : Benzene, ppbv
M =59F (15C)
Soil Type: Clay Sampling Date: 5/22/2003 8/23/2003 Ambient Temp, o C 21.7 o C 37.8 o C Default Temp*, o C 15 o C 15 o C Est.Temp**, o C,3.9m, bgs 15 o C 31.5 o C Est.Temp**, o C,4.5m, btoc 15 o C 31 o C *Figure 1, 2001EPA Fact Sheet ** Estimated soil temp using software
SG-SCREEN Version 3.1; 02/04 Reset to Defaults Soil Gas Concentration Data ENTER ENTER ENTER Soil Soil Chemical gas OR gas CAS No. conc., conc., (numbers only, C g C g no dashes) (μg/m 3 ) (ppmv) Chemical 71432 2.40E+01 Benzene ENTER ENTER ENTER ENTER ENTER Depth MORE below grade Soil gas Vadose zone User-defined to bottom sampling Average SCS vadose zone of enclosed depth soil soil type soil vapor space floor, below grade, temperature, (used to estimate OR permeability, L F L s T S soil vapor k v (15 or 200 cm) (cm) ( o C) permeability) (cm 2 ) 15 390 15 C ENTER ENTER ENTER ENTER ENTER MORE Vandose zone Vadose zone Vadose zone Vadose zone Average vapor SCS soil dry soil total soil water-filled flow rate into bldg. soil type bulk density, porosity, porosity, (Leave blank to calculate) Lookup Soil A ρ b n V V θ w Q soil Parameters (g/cm 3 ) (cm 3 /cm 3 ) (L/m) C 1.43 0.459 0.215 5 MORE ENTER ENTER ENTER ENTER Averaging Averaging time for time for Exposure Exposure carcinogens, noncarcinogens, duration, frequency, AT C AT NC ED EF (yrs) (yrs) (yrs) (days/yr) END 70 30 30 350
Benzene in Soil Gas INCREMENTAL RISK CALCULATIONS: Incremental risk from vapor carcinogen 1.4E-04 Hazard quotient from vapor noncarcinogen 1.4E+00 5/19/2003, soil gas = 24,000 ppbv, 15C INCREMENTAL RISK CALCULATIONS: INCREMENTAL RISK CALCULATIONS: Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen 2.4E-05 2.4E-01 2.2E-05 2.2E-01 8/23/2003, soil gas = 4,200 ppbv, 15C 8/23/2003, soil gas = 4,200 ppbv, 31.5C
Benzene in Groundwater INCREMENTAL RISK CALCULATIONS: INCREMENTAL RISK CALCULATIONS: Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen 6.8E-06 6.8E-02 1.0E-05 1.0E-01 8/23/2003, GW= 646 ug/l, 15C 8/23/2003, GW = 646 ug/l, 31C
COC Benzene Sampling Date: 5/19/2003 8/23/2003 Soil gas, 3.9m bgs, ppbv 24,000 4,200 Risk default temp, 15 o C. 1x 10-4 2x 10-5 Risk est. temp, 15 o C 1x 10-4 Riskest. temp, 31.5oC 2x 10-5 Groundwater, 4.5m btoc, ug/l 818 646 Risk default temp, 15 o C 9x 10-6 7x 10-6 Risk est. temp, 15 o C 9x 10-6 Riskest temp, 31oC 1x 10-5
Site B- Midwest City, OK Combined Groundwater PCE/TCE plume
X=62F (16.6C)
Sampling Date: 12/21/2004 Soil type: silt/siltstone Ambient Temp, o C 10 o C Default Temp*, o C 16.6 o C Est.Temp**, o C, 2.44m bgs 3.5 o C Est.Temp**, o C, 9.15m btoc 5 o C *Figure 1, 2001 EPA Fact Sheet ** Estimated soil temp. using software
SG-SCREEN Version 3.1; 02/04 Reset to Defaults Soil Gas Concentration Data ENTER ENTER ENTER Soil Soil Chemical gas OR gas CAS No. conc., conc., (numbers only, C g C g no dashes) (μg/m 3 ) (ppmv) Chemical 127184 9.40E-02 Tetrachloroethylene ENTER ENTER ENTER ENTER ENTER Depth MORE below grade Soil gas Vadose zone User-defined to bottom sampling Average SCS vadose zone of enclosed depth soil soil type soil vapor space floor, below grade, temperature, (used to estimate OR permeability, L F L s T S soil vapor k v (15 or 200 cm) (cm) ( o C) permeability) (cm 2 ) 15 244 16.6 SI ENTER ENTER ENTER ENTER ENTER MORE Vandose zone Vadose zone Vadose zone Vadose zone Average vapor SCS soil dry soil total soil water-filled flow rate into bldg. soil type bulk density, porosity, porosity, (Leave blank to calculate) Lookup Soil A ρ b n V V θ w Q soil Parameters (g/cm 3 ) (cm 3 /cm 3 ) (L/m) SI 1.35 0.489 0.167 5 MORE ENTER ENTER ENTER ENTER Averaging Averaging time for time for Exposure Exposure carcinogens, noncarcinogens, duration, frequency, AT C AT NC ED EF (yrs) (yrs) (yrs) (days/yr) END 70 30 30 350
Tetrachloroethylene Soil Gas INCREMENTAL RISK CALCULATIONS: INCREMENTAL RISK CALCULATIONS: Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen 2.1E-06 1.4E-03 2.2E-06 1.4E-03 Soil gas = 94 ppbv, 16.6C Soil gas = 94 ppbv, 3.5C Trichloroethylene INCREMENTAL RISK CALCULATIONS: INCREMENTAL RISK CALCULATIONS: Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen 2.3E-04 1.2E-01 2.5E-04 1.3E-01 Soil gas = 670 ppbv, 16.6C Soil gas = 670 ppbv, 3.5C
Tetrachloroethylene Groundwater INCREMENTAL RISK CALCULATIONS: INCREMENTAL RISK CALCULATIONS: Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen 2.8E-06 1.8E-03 1.6E-06 1.1E-03 GW = 280 ug/l, 16.6 C GW = 280 ug/l, 5C Trichloroethylene INCREMENTAL RISK CALCULATIONS: INCREMENTAL RISK CALCULATIONS: Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen Incremental risk from vapor carcinogen Hazard quotient from vapor noncarcinogen 1.1E-06 5.6E-04 7.0E-07 3.7E-04 GW = 8.29 ug/l, 16.6C GW = 8.29 ug/l, 5C
Sampling Date: 12/21/2004 COC: PCE TCE Soil gas, 2.5m bgs, ppbv 94 670 Risk o default temp, 16.6 C 2 x 10-6 3 x 10-4 Risk est.temp, 3.5 o C 2 x 10-6 2 x 10-4 Groundwater, 9.15m, btoc, ug/l 280 8.29 Risk default temp, 16.6 o C 3 x 10-6 1 x 10-6 Risk est.temp, 5 o C 2 x 10-6 7 x 10-7
So, Incremental risk from Groundwater Screening Model seem to be affected by changes in soil temperature.
but, not the Soil Gas Screening model. But is soil gas not really affected by soil temperature?
In the light of these observations, Are the risk levels from the J&E model acceptable, even if we use site specific values?
Lastly, if multiple lines of evidence will be considered in the evaluation, Maybe, it is prudent to check and give prime consideration to the Acceptability of the values and methods from where they were derived.
We can start with the J&E model.
Thank you!