Presentation to the Moffett Field Restoration Advisory Board, September 9, 2010: EPA Vapor Intrusion Update, Alana Lee, EPA

1. EPA Vapor Intrusion Update
Former NAS M ff tt Fi ld
F Moffett Field
Restoration Advisory Board Meeting
September 9, 2010
Alana Lee
EPA Region 9

2. Five-Year Review Follow-up Actions to
Ensure the Protectiveness of the Remedy
Vapor Intrusion
• Finalize the ROD Amendment for the vapor intrusion
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pathway.
y
• Complete baseline sampling and evaluation of
buildings within the Vapor Intrusion Study Area
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Implement remedial actions on buildings, as needed.
t di l ti b ildi d d
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3. EPA Five-Year Review
Protectiveness Assessment
• The remedy at Site 28, WATS Area, is NOT protective
because 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 health
health.
• The vapor intrusion remedy will be incorporated into
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the overall MEW Site remedy through an Amendment
to the 1989 MEW Record of Decision (ROD).

4. Milestones
• EPA issued Proposed Plan
Public C
P bli Comment Period July 10 – N 7 2009
tP i dJ l Nov 7,
• EPA carefully considered all comments
f ll id d ll t
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.
• ROD Amendment includes responses to
comments in a Responsiveness Summary
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5. Vapor Intrusion Pathway
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6. MEW and NAS Moffett Field Site Location and Vapor Intrusion Study Area

7. Vapor Intrusion Study Area
• All buildings overlying the shallow groundwater
contamination
t i ti
• Defined by the area where TCE concentrations
in h ll
i shallow groundwater are greater than 5
d t t th
micrograms per liter (ug/L), or parts per billion
(ppb)
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8. Estimated Extent of TCE in Shallow Groundwater & Vapor Intrusion
Study Area

9. Scope and Role of Response Action
• Response actions will address the potential health risks
associated with long-term exposure to TCE and other
long term
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 as
concern,
tetrachloroethene (PCE) and vinyl chloride to enter indoor air
exceeding indoor air cleanup levels for long-term exposure).
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10. Response Action Tiering System for
Existing Buildings
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(Sampled with Passive or Active Engineering Control in Place
or Operating)
Tier Description
Tier 1 Indoor air concentrations greater than outdoor
(background)
(background)* air concentrations and indoor air
cleanup level.
Tier 2 Indoor air concentrations below the indoor air
cleanup l
l levels.
l
Former Tier 1 existing building and Tier A future
(
(new) building that confirmed indoor air
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concentrations are below the indoor air cleanup
levels.
* Outdoor concentrations of TCE typically range from below laboratory analytical detection limits to 0.4
mg/m3.

11. Response Action Tiering System for Buildings
(Sampled with No Engineering Control in Place or
Operating)
Building Description
Tier
Tier 1 Indoor air concentrations greater than outdoor
(background)* air concentrations and indoor air cleanup
level.
level
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.
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* Outdoor concentrations of TCE typically range from below laboratory analytical detection limits to 0.4
mg/m3.

12. Purpose of Institutional Controls
• Ensure engineering controls used to prevent indoor air
contaminant levels from reaching EPA’s cleanup level are
implemented, operated, and monitored as required b th
i l t d t d d it d i d 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 remedy
owners, managers,
and its requirements
• Inform responsible parties and EPA when building
ownership or building configuration changes
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13. EPA’s Selected Vapor Intrusion Remedy
Building Scenario Selected Remedy
Existing Buildings
Tier
Ti 1 and Tier 2 Buildings
d Ti B ildi Active Sub-slab/Sub-membrane Ventilation,
A ti S b l b/S b b V til ti
Monitoring, and ICs *
Tier 3A and 3B Buildings No Engineering Control. Monitoring and ICs
Tier 4 Building No remedy required
Future Buildings
Tier
Ti A Passive Sub-Slab Ventilation with Vapor Barrier (and
P i S b Sl b V til ti ith V B i ( d
Ability to Convert to Active), Monitoring, and ICs
Tier B No remedy required
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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14. 14

15. What Happens Next
• Implement the vapor intrusion remedy
- EPA preparing work requirements
i k i t
- Di
Discussions with MEW Responsible Parties,
i ith R ibl P ti
Navy, and NASA to conduct the work
• Continued community involvement activities
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16. For More Information
MEW and Moffett Field Site information and Vapor Intrusion
Resources and files:
EPA websites:
www.epa.gov/region9/mew
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www.epa.gov/region9/moffettfield
www.epa/oswer/vaporintrusion
Alana Lee
415.972.3141
Lee.Alana@epa.gov
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