RAB Vapor Intrusion Mitigation
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This presentation discussed vapor intrusion mitigation methods being used at the former Naval Air Station Moffett Field. It outlined three main vapor intrusion mitigation methods: eliminating preferential pathways beneath buildings by sealing cracks and openings; increasing ventilation inside buildings; and using active sub-slab ventilation systems to depressurize below slabs and prevent soil gas from entering. Confirmation air sampling would be conducted after mitigation to verify the effectiveness of these methods in reducing indoor air contaminant levels below cleanup standards. A vapor intrusion mitigation work plan was in development with field work scheduled from fall 2017 to spring 2018 and completion reporting in 2018.
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RAB Vapor Intrusion Mitigation
- 1. ACTIVITY NAME Vapor Intrusion Mitigation Former Naval Air Station Moffett Field Restoration Advisory Board Meeting May 11, 2017 Wilson Doctor Navy Project Manager
- 2. 5 BRAC Program Management Office. Vapor Intrusion Mitigation Schematic of Vapor Intrusion Pathway
- 3. 6 BRAC Program Management Office. Vapor Intrusion Mitigation Methods Vapor Intrusion Mitigation Methods – Eliminate preferential pathways – Increase ventilation inside the building – Active sub-slab ventilation (depressurization)
- 4. 7 BRAC Program Management Office. Vapor Intrusion Mitigation Methods Eliminate Preferential Pathways – Fill subsurface vaults – Seal cracks/expansion joints in floor slabs – Seal pipe penetrations/floor drains Sealing floor cracks Sealing floor drains
- 5. 5 BRAC Program Management Office. Vapor Intrusion Mitigation Schematic of Vapor Intrusion Pathway
- 6. 6 BRAC Program Management Office. Vapor Intrusion Mitigation Methods Vapor Intrusion Mitigation Methods – Eliminate preferential pathways – Increase ventilation inside the building – Active sub-slab ventilation (depressurization)
- 7. 7 BRAC Program Management Office. Vapor Intrusion Mitigation Methods Eliminate Preferential Pathways – Fill subsurface vaults – Seal cracks/expansion joints in floor slabs – Seal pipe penetrations/floor drains Sealing floor cracks Sealing floor drains
- 8. 8 BRAC Program Management Office. Vapor Intrusion Mitigation Methods Increase Ventilation Inside the Building – Fresh air intake – Increased air exchange rate
- 9. 9 BRAC Program Management Office. Vapor Intrusion Mitigation Methods Active Sub-slab Ventilation – Sub-slab depressurization system creates a negative pressure field below the building preventing soil gas from entering the building Schematic Sub-Slab Depressurization System Sub-Slab Depressurization Blower and Vent
- 10. 10 BRAC Program Management Office. Confirmation Sampling ROD Amendment for the Vapor Intrusion Pathway (EPA, 2010) for long-term exposure Chemical of Concern Indoor Air Cleanup Level (µg/m3) Commercial Trichloroethene (TCE) 5 Perchloroethylene (PCE) 2 cis-1,2-Dichloroethene 210 trans-1,2-Dichloroethene 210 Vinyl Chloride 2 1,1-Dichloroethane 6 1,1-Dichloroethene 700 Following implementation of mitigation measures, conduct air sampling to verify effectiveness.
- 11. 11 BRAC Program Management Office. Current Status and Schedule • Vapor Intrusion Mitigation Work Plan – Draft submitted March 17, 2017 – Final scheduled for Summer 2017 • Vapor Intrusion Mitigation Field Work – Scheduled for Fall 2017 through Spring 2018 • Completion Report – Draft scheduled for Summer 2018 – Final Scheduled for Winter 2018
- 12. 12 BRAC Program Management Office. Vapor Intrusion Mitigation QUESTIONS ?