Presentation to the Moffett Restoration Advisory Board on February 13, 2014 by Scott Anderson of the Navy

1. ACTIVITY NAME
Vapor Intrusion Update
Former Naval Air Station Moffett Field
Restoration Advisory Board Meeting
February 13, 2014

2. Update Topics
• Background
• Past activities
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May-June 2012 Indoor Air Sampling
Building 10 Utility Corridor Interim Action
May 2013 Vapor Pathway Investigation
May-June 2013 Soil Gas and Groundwater
Investigation
• Current sampling
– February 2014 Indoor Air Sampling
• Next steps
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3. Site Background
Navy (yellow), NASA (blue) and MEW Areas of Responsibility (green)
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BRAC Program Management Office.

4. Indoor Air Cleanup Levels
Chemical of Concern
Indoor Air Cleanup
Level (mg/m3)
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
Commercial
ROD Amendment for the Vapor Intrusion Pathway (EPA, 2010)
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5. May-June 2012 Sampling
• Sampled indoor air in 23 commercial buildings to identify
areas with COCs that exceed ROD cleanup levels
• Visually inspected all buildings within the Navy area that
are occupied or may be occupied – Nov 2011 and Apr
2012
• Interviewed building managers about building use,
operations, work hours for occupants, etc.
• Obtained information on heating, ventilation and air
conditioning (HVAC) system operations and chemicals
used in the buildings
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6. Air Sampling Scope
• Buildings with HVAC systems were sampled with HVAC on and
off
• HVAC-off samples were collected over Memorial Day weekend
• Buildings without HVACs were sampled with windows and doors
shut when possible
• Sampled work areas and
pathways (crawl spaces,
utility conduits, elevator
shafts, stairwells)
• Collected 29 ambient air
(outdoor/background)
samples
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BRAC Program Management Office.

7. Results for Air Sampling
• Majority of buildings had detected VOCs above outdoor air
levels but below action levels.
• Only Buildings 10 and 126 had multiple samples that had
VOCs above action levels. A groundwater investigation was
conducted in 2012 and 2013 to investigate the VOC source
near Building 126 (Site 28).
• Buildings 3, 12, N210, and N239A (pathway locations) had
samples from a single location that had a VOC exceeding
project action levels. None of the samples collected from the
work areas in these buildings exceeded the ROD action levels.
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8. Building 10
• Chlorinated solvent vapors were detected in Building 10 above
action levels in the Vapor Intrusion ROD Amendment.
• The solvent vapors result from solvents that are dissolved in
the shallow groundwater. The primary vapor intrusion
pathway is through the utility corridor connected to Building
10.
• A blower system has been
installed in the utility
corridor as an interim
measure to reduce
migration of vapors from the
corridor into Building 10.
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BRAC Program Management Office.

9. Building 10 Response Actions & Air Monitoring
• Check work area air quality monthly using field measurement
instruments and quarterly using air canisters.
• Air monitoring results in February 2013 indicated TCE was still
near ROD cleanup levels near the corridor entrance in Building 10
but below cleanup levels in the work area. Therefore,
modifications were made to the system in May 2013:
– Installed a barrier wall at the
corridor entrance
– Installed a second blower in the
Building 10 floor trench that
connects to the corridor.
• Sampled Building 10 in June and
November 2013
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BRAC Program Management Office.

10. Building 10 Response Actions & Air Monitoring
• Indoor air concentrations in the work areas were below action
levels (TCE 0.89 to 1.1 mg/m3).
• The blower system successfully reduced indoor air
concentrations.
• The blower system will remain in place as an interim measure
until long-term plans are implemented.
• The utility corridor is being evaluated to develop potential
closure/sealing options.
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11. Vapor Pathway Investigation
• Follow-up indoor air sampling was conducted in May-June 2013 to
evaluate floor conduit vapor pathways in Buildings 2, 3, and 12 and a
TCE detection in Building N239A.
• In Buildings 2, 3 and 12, floor utility conduits
were sealed as an interim measure at pathway
locations where elevated TCE was detected in
May 2012 . Indoor air samples were collected at
these locations before sealing and again 1 to 2
weeks after.
• Sealing was effective for Building 2 which does
not have an HVAC.
• Sealing had limited effectiveness in Buildings 3
and 12, both of which have HVAC systems.
Building 12
Room 110
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Building 3
Room 130

12. Vapor Pathway Investigation
• In Building N239A, two utility rooms (intermittent work areas)
were inspected for solvent sources and vapor pathways.
• Floor conduits were found in the
utility rooms.
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BRAC Program Management Office.

13. Soil Gas and Groundwater Investigation
June 2013: Collected 56 soil gas and 20 groundwater samples
around the perimeter of buildings and along the Building 10
utility corridor to investigate shallow groundwater as a vapor
source and potential vapor pathways in soil.
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14. Soil Gas and Groundwater Investigation
Soil Gas
• Installed soil gas probes above the water table
• Probes sampled after 48 hours
• Samples were analyzed using a mobile lab.
Groundwater
• Installed temporary groundwater wells 2
feet into groundwater.
• Samples were collected with a bailer and
not filtered.
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15. Soil Gas Results
• TCE and related degradation products are primarily limited to the
vicinities of Buildings 3, 10, 15, 16, 45, 76, 126, 555, 567 and the utility
corridor from Building 10.
• Isolated areas exist in the vicinities of Buildings 2, 14, N210 and 239A.
(mg/m3)
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16. Groundwater Results
•PCE only detected above MCL at Building 126.
•TCE above 500 mg/L near Buildings 10, 76, 126 and N210.
•Other COCs are high near Buildings 10, 29, 76, 126 and N210.
(mg/L)
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17. February 2014 Air Sampling
• A 2nd series of indoor and outdoor air samples will be
collected during February 11 – 18, 2014.
• This sampling will provide data on potential seasonal
differences on the occurrence of vapor intrusion.
• The winter data from February 2014 will be compared to the
late-spring data from May-June 2012.
• Indoor air samples will only be collected from the basement
and 1st floor of the 23 buildings during the February 2014
sampling.
• As in 2012, samples collected in February 2014 will be
collected with both the HVAC on and off.
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18. Vapor Intrusion Tier Response Evaluation
•Data collected in 2012, 2013 and 2014 will be evaluated
and used to rank the buildings according to the Vapor
Intrusion ROD Amendment.
•Response actions for each building will be developed.
– Engineering controls, institutional controls, monitoring
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19. Future Activities
•The building tiering evaluation will be included in the
February 2014 sampling results report. The draft report is
scheduled for late June 2014.
•Continue with CERCLA process for Remedial Design and
Remedial Action
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20. Air Sampling for Vapor Intrusion
QUESTIONS ?
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