Presentation to the Moffett Restoration Advisory Board May 11, 2017.

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 ?