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 ?