EPA Vapor Intrusion Update

F NAS M ff tt Fi ldFormer NAS Moffett FieldRestoration Advisory Board Meeting

September 9, 2010

Alana LeeAlana LeeEPA Region 9

Five-Year Review Follow-up Actions to Ensure the Protectiveness of the Remedy

Vapor Intrusion

• Finalize the ROD Amendment for the vapor intrusion pathway.p y

• Complete baseline sampling and evaluation of buildings within the Vapor Intrusion Study AreaI l t di l ti b ildi d d• Implement remedial actions on buildings, as needed.

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EPA Five-Year Review Protectiveness Assessment• The remedy at Site 28, WATS Area, is NOT protective

because it does not adequately address the potentialbecause it does not adequately address the potential long-term health risks from TCE from the vapor intrusion pathway.

• Remedial actions are necessary to ensure the protection of human healthprotection of human health.

• The vapor intrusion remedy will be incorporated into p y pthe overall MEW Site remedy through an Amendment to the 1989 MEW Record of Decision (ROD).

Milestones

• EPA issued Proposed PlanP bli C t P i d J l 10 N 7 2009Public Comment Period July 10 – Nov 7, 2009

EPA f ll id d ll t• EPA carefully considered all comments received during the public comment period

• EPA selected vapor intrusion remedy in an amendment to EPA’s 1989 Record of Decision (ROD Amendment) on August 16, 2010.

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• ROD Amendment includes responses to comments in a Responsiveness Summary

Vapor Intrusion Pathway

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MEW and NAS Moffett Field Site Location and Vapor Intrusion Study Area

Vapor Intrusion Study Area

• All buildings overlying the shallow groundwater t i ticontamination

• Defined by the area where TCE concentrations i h ll d t t th 5in shallow groundwater are greater than 5 micrograms per liter (ug/L), or parts per billion (ppb)(ppb)

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Estimated Extent of TCE in Shallow Groundwater & Vapor Intrusion Study Area

Scope and Role of Response Action

• Response actions will address the potential health risks associated with long term exposure to TCE and otherassociated with long-term exposure to TCE and other Site contaminants.

• TCE is the primary chemical of concern for the vapor intrusion pathway at the MEW Site (although there is the potential for other MEW Site chemicals of concern such aspotential for other MEW Site chemicals of concern, such as tetrachloroethene (PCE) and vinyl chloride to enter indoor air exceeding indoor air cleanup levels for long-term exposure).

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Response Action Tiering System forExisting Buildingsg g

(Sampled with Passive or Active Engineering Control in Place or Operating)

Tier DescriptionTier 1 Indoor air concentrations greater than outdoor

(background)* air concentrations and indoor air(background) air concentrations and indoor air cleanup level.

Tier 2 Indoor air concentrations below the indoor air l l lcleanup levels.

Former Tier 1 existing building and Tier A future (new) building that confirmed indoor air ( ) gconcentrations are below the indoor air cleanup levels.

* Outdoor concentrations of TCE typically range from below laboratory analytical detection limits to 0.4 mg/m3.

Response Action Tiering System for Buildings(Sampled with No Engineering Control in Place or

Building Tier

DescriptionOperating)

TierTier 1 Indoor air concentrations greater than outdoor

(background)* air concentrations and indoor air cleanup levellevel.

Tier 3A Indoor air concentrations below indoor air cleanup levels, but greater than outdoor (background) concentrations.

Tier 3B Building with indoor air concentrations at or within outdoor air (background)* concentrations.

Tier 4 Buildings where converging lines of evidence demonstrate that there is no longer the potential for vapor intrusion into the building exceeding indoor air cleanup levels.g g p

* Outdoor concentrations of TCE typically range from below laboratory analytical detection limits to 0.4 mg/m3.

Purpose of Institutional Controls

• Ensure engineering controls used to prevent indoor air contaminant levels from reaching EPA’s cleanup level are i l t d t d d it d i d b thimplemented, operated, and monitored as required by the remedy

• Access to install and operate stand-alone building remedy, as necessary

• Ensure appropriate remedy installed in new development

• Inform building owners managers and occupants of remedyInform building owners, managers, and occupants of remedy and its requirements

• Inform responsible parties and EPA when building

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• Inform responsible parties and EPA when building ownership or building configuration changes

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EPA’s Selected Vapor Intrusion Remedy

Building Scenario Selected RemedyExisting BuildingsTi 1 d Ti 2 B ildi A ti S b l b/S b b V til tiTier 1 and Tier 2 Buildings Active Sub-slab/Sub-membrane Ventilation,

Monitoring, and ICs *

Tier 3A and 3B Buildings No Engineering Control. Monitoring and ICs

Tier 4 Building No remedy required

Future BuildingsTi A P i S b Sl b V til ti ith V B i ( dTier A Passive Sub-Slab Ventilation with Vapor Barrier (and

Ability to Convert to Active), Monitoring, and ICs

Tier B No remedy requiredTier B No remedy required

Notes:

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Notes:* Alternatively, Active Indoor Air Ventilation System, Monitoring, and ICs (including conduit sealing) may be selected as the vapor intrusion remedy for Tier 1 and 2 existing commercial buildings if the property/building owner agrees to use, operate, and monitor the indoor air ventilation system (e.g., HVAC) in a manner consistent with the operations, maintenance, and monitoring plan developed for that building, in a signed recorded agreement.

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What Happens Next

• Implement the vapor intrusion remedyEPA i k i t- EPA preparing work requirements

Di i ith MEW R ibl P ti- Discussions with MEW Responsible Parties, Navy, and NASA to conduct the work

• Continued community involvement activities

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For More Information

MEW and Moffett Field Site information and Vapor Intrusion Resources and files:

EPA websites: www.epa.gov/region9/mewp g gwww.epa.gov/region9/moffettfieldwww.epa/oswer/vaporintrusion

Alana Lee415.972.3141415.972.3141Lee.Alana@epa.gov

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