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Lutes panel discussion conf battelle2016 power_point_template_widescreenrev
- 2. 2Delivering Sustainable Solutions to Complex Local Challenges, Worldwide © 2016 CH2M Topics • Hydrogeology and Henry’s Law Calculations • Soil Gas Trend vs. Depth • Attenuation Factors Subslab/Indoor Air • Advective Driving Force from Deep Soil Gas • Effect of March 2011 Sealing of First Floor Drain on Dataset • Helium Tracer Testing • Potential for Preferential Pathways at Multiple Scales • Geophysics
- 4. 4Delivering Sustainable Solutions to Complex Local Challenges, Worldwide © 2016 CH2M Henry’s Law Analysis – Is Source Groundwater? • Reasonable agreement between the observed deep soil gas PCE concentrations and those predicted by Henry’s law • Chloroform is generally more concentrated in the deep soil gas than in groundwater. • Suggests: (1) PCE is migrating to the immediate vicinity of the house in groundwater and vapor intrusion is driven by transport from groundwater and (2) chloroform is arriving at the immediate vicinity of the house at least in part from other sources, such as a buried storm sewer or sewer main.
- 15. 15Delivering Sustainable Solutions to Complex Local Challenges, Worldwide © 2016 CH2M Tracer Test Procedures • Helium injected to 13 ft exterior soil gas location, deepest depth normally above water table • 18 to 26 liter injections • Tests 1 & 2 injection in front yard tests3 & 4 injection in the back yard • The mitigation system was on during tests 2 and 4 15
- 16. 16Delivering Sustainable Solutions to Complex Local Challenges, Worldwide © 2016 CH2M Tracer Tests Conclusions • The variability between paired tests (mitigation on and mitigation off) was more pronounced beneath the building where the mitigation system would be expected to have the most significant influence on airflow. • The highest concentrations observed were usually those close to the 13-ft deep injection depth, suggesting attenuation as the tracer migrated upward. • The high concentrations observed at the 9-ft and 13-ft depths for all the injections, despite the buoyancy of the helium-enriched soil gas, suggest that transference of helium is easy horizontally toward the building over distances of up to 20 ft typically within 2 days. • Vertical migration from 13 ft to 6 ft bls also occurred relatively rapidly at the injection cluster. • In all cases, tracer concentrations were reduced to baseline concentrations within 2–2.5 days, indicating a rather quick clearing out of trace gas from the subsurface under mitigated and non- mitigated conditions.
- 18. 18Delivering Sustainable Solutions to Complex Local Challenges, Worldwide © 2016 CH2M Geophysics Observations • 422 basement, 500 MHz GPR South to North • Shows evidence of filled cistern and doorway Doorwa y Cistern
- 19. 19Delivering Sustainable Solutions to Complex Local Challenges, Worldwide © 2016 CH2M Geophysics Observations • 422Basement 900 MHz GPR South North • Shows evidence of depth of sewer line under slab • Interior GPR suggests the concrete slab varies from 0.5 to 0.7 feet with undulating contact with underlying materials • Suggests concrete not poured on flattened fill
- 20. 20Delivering Sustainable Solutions to Complex Local Challenges, Worldwide © 2016 CH2M Summary • Henry’s law analysis suggests deep soil gas and groundwater agree for PCE, not so well for chloroform • Pattern of PCE different at exterior and interior soil gas clusters; • Subslab to indoor attenuation factors in line with expectations for building of this age • Subslab to indoor air attenuation factors similar for PCE, chloroform and radon • Advective driving force present from deep to subbasement soil gas • Chloroform on first floor clearly influenced by floor drain before sealing in March 2011 • Sealing efforts did not effect PCE trend in indoor air • Tracer test shows rapid movement from deep soil gas to subslab • Potential preferential pathway influences should be evaluated at multiple scales – neighborhood, lot and building envelope • Geophysics mapped sewer line and cistern 20
- 21. 21Delivering Sustainable Solutions to Complex Local Challenges, Worldwide © 2016 CH2M Acknowledgements and Information Sources Data discussed today was collected with EPA NERL Funding – Brian Schumacher and John Zimmerman, PIs. Today’s discussions of the data set have not been EPA reviewed. EPA reviewed reports are available for more information: First: “Fluctuation Of Indoor Radon And VOC Concentrations Due To Seasonal Variations” http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P100KK1J.txt Second: “Assessment of Mitigation Systems on Vapor Intrusion: Temporal Trends, Attenuation Factors, and Contaminant Migration Routes under Mitigated and Non-mitigated Conditions” http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=308904 • Third: “Simple, Efficient, and Rapid Methods to Determine the Potential for Vapor Intrusion into the Home: Temporal Trends, Vapor Intrusion Forecasting, Sampling Strategies, and Contaminant Migration Routes” http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=309644 • And a Fourth as a Journal Article: Lutes, C. C., Truesdale, R. S., Cosky, B. W., Zimmerman, J. H., & Schumacher, B. A. (2015). Comparing Vapor Intrusion Mitigation System Performance for VOCs and Radon. Remediation Journal, 25(4), 7-26.