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Presentation to the Moffett Restoration Advisory Board on February 13, 2014 by EPA's Alana Lee and Penny Reddy
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EPA Vapor Intrusion Update
Former NAS Moffett FieldRestoration Advisory Board Meeting
February 13, 2014
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MEWArea
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MEW Area – CommercialBuildings Summary
• Over 66 buildings sampled in MEW Area – South of101.
• Interim vapor intrusion control measures taken –when indoor air or pathway concentrations exceededTCE indoor air cleanup level of 5 micrograms percubic meter (e.g., seal conduits, modify buildingventilation system, install sub-slab or crawlspacevapor mitigations system).
• New commercial buildings built with vapor intrusioncontrol systems
= TCE Hot Spot Area
Indoor Air Sampling ResultsSummary
• EPA sampled over 90 residences in expandedresidential areas, and over 140 residences
• No TCE was detected in most residences sampled.
• TCE was detected in some residences, but belowindoor air cleanup levels. These homes were re-sampled to confirm TCE below indoor air cleanuplevels.
• TCE was found in only two residences exceedingEPA’s TCE indoor air cleanup level of 1 microgramper cubic meter.
• Vapor intrusion control systems were installed tomitigate TCE indoor air concentrations to belowindoor air cleanup levels.
Summary
• Results from all indoor air sampling showed vaporintrusion not a problem in most residences sampled.
• Based on groundwater and air sampling to date,areas outside the high priority areas that overlie lowerTCE groundwater concentrations are considered aslow vapor intrusion risk.
Ongoing and UpcomingWork
• Ongoing vapor intrusion sampling in commercialbuildings.
• EPA planning additional subsurface investigation thisspring, which will include groundwater and soil gassampling along Fairchild Drive.
• EPA will continue to update the community on theplanned work and our findings
• EPA conducting streamlined Five-Year Review forthe MEW Site.
EPA Contact Information
Alana Lee
EPA Project Manager - Vapor Intrusion & Potential Source Investigation
415.972.3141
Penny Reddy
EPA Project Manager – Groundwater Cleanup
415.972.3108
Alejandro Diaz
EPA Community InvolvementCoordinator
415.972.3242
EPA Websites –For More Informationwww.epa.gov/region9/mewwww.epa.gov/region9/moffettfieldwww.epa.gov/oswer/vaporintrusion
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