ACTIVITY NAME

Vapor Intrusion MitigationFormer Naval Air Station Moffett Field

Restoration Advisory Board Meeting May 11, 2017

Wilson DoctorNavy Project Manager

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Vapor Intrusion MitigationSchematic of Vapor Intrusion Pathway

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Vapor Intrusion Mitigation Methods

Vapor Intrusion Mitigation Methods

– Eliminate preferential pathways

– Increase ventilation inside the building

– Active sub-slab ventilation (depressurization)

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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

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Vapor Intrusion Mitigation Methods

Increase Ventilation Inside the Building– Fresh air intake – Increased air exchange rate

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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

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Confirmation Sampling

ROD Amendment for the Vapor Intrusion Pathway (EPA, 2010) for long-term exposure

Chemical of ConcernIndoor 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.

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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

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Vapor Intrusion Mitigation

QUESTIONS ?